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arm64: Early CPU feature override, and applications to VHE, BTI and PAuth

PATCH Superseded Marc Zyngier 4 participants 32 messages Jan 11, 2021 – Jan 12, 2021

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v3 of 7 Superseded Latest is v7 →

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Marc Zyngier

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v3 cover arm64: Early CPU feature override, and applications to VHE, BTI and PAuth

It recently came to light that there is a need to be able to override some CPU features very early on, before the kernel is fully up and running. The reasons for this range from specific feature support (such as using Protected KVM on VHE HW, which is the main motivation for this work) to errata workaround (a feature is broken on a CPU and needs to be turned off, or rather not enabled).

This series tries to offer a limited framework for this kind of problems, by allowing a set of options to be passed on the command-line and altering the feature set that the cpufeature subsystem exposes to the rest of the kernel. Note that this doesn't change anything for code that directly uses the CPU ID registers.

The series completely changes the way a VHE-capable system boots, by *always* booting non-VHE first, and then upgrading to VHE when deemed capable. Although it sounds scary, this is actually simple to implement (and I wish I had done that five years ago). The "upgrade to VHE" path is then conditioned on the VHE feature not being disabled from the command-line.

Said command-line parsing borrows a lot from the kaslr code, and subsequently allows the "nokaslr" option to be moved to the new infrastructure (though it all looks a bit... odd).

Further patches now add support for disabling BTI and PAuth, the latter being based on an initial series by Srinivas Ramana[0].

This has been tested on multiple VHE and non-VHE systems.

* From v2 [2]:
- Simplify the VHE_RESTART stub
- Fixed a number of spelling mistakes, and hopefully introduced a few more
- Override features in __read_sysreg_by_encoding()
- Allow both BTI and PAuth to be overridden on the command line
- Rebased on -rc3

* From v1 [1]:
- Fix SPE init on VHE when EL2 doesn't own SPE
- Fix re-init when KASLR is used
- Handle the resume path
- Rebased to 5.11-rc2

[0] https://lore.kernel.org/r/[email protected]
[1] https://lore.kernel.org/r/[email protected]
[2] https://lore.kernel.org/r/[email protected]

Marc Zyngier (20):
arm64: Fix labels in el2_setup macros
arm64: Fix outdated TCR setup comment
arm64: Turn the MMU-on sequence into a macro
arm64: Provide an 'upgrade to VHE' stub hypercall
arm64: Initialise as nVHE before switching to VHE
arm64: Move VHE-specific SPE setup to mutate_to_vhe()
arm64: Simplify init_el2_state to be non-VHE only
arm64: Move SCTLR_EL1 initialisation to EL-agnostic code
arm64: cpufeature: Add global feature override facility
arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding()
arm64: Extract early FDT mapping from kaslr_early_init()
arm64: cpufeature: Add an early command-line cpufeature override
facility
arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command
line
arm64: Honor VHE being disabled from the command-line
arm64: Add an aliasing facility for the idreg override
arm64: Make kvm-arm.mode={nvhe,protected} an alias of

    id_aa64mmfr1.vh=0

KVM: arm64: Document HVC_VHE_RESTART stub hypercall
arm64: Move "nokaslr" over to the early cpufeature infrastructure
arm64: cpufeatures: Allow disabling of BTI from the command-line
arm64: cpufeatures: Allow disabling of Pointer Auth from the
command-line

Srinivas Ramana (1):
arm64: Defer enabling pointer authentication on boot core

 .../admin-guide/kernel-parameters.txt         |   9 +
 Documentation/virt/kvm/arm/hyp-abi.rst        |   9 +
 arch/arm64/include/asm/assembler.h            |  17 ++
 arch/arm64/include/asm/cpufeature.h           |  10 +
 arch/arm64/include/asm/el2_setup.h            |  60 ++----
 arch/arm64/include/asm/pointer_auth.h         |  10 +
 arch/arm64/include/asm/setup.h                |  11 +
 arch/arm64/include/asm/stackprotector.h       |   1 +
 arch/arm64/include/asm/virt.h                 |   7 +-
 arch/arm64/kernel/Makefile                    |   2 +-
 arch/arm64/kernel/cpufeature.c                |  57 ++++-
 arch/arm64/kernel/head.S                      |  75 ++-----
 arch/arm64/kernel/hyp-stub.S                  | 124 ++++++++++-
 arch/arm64/kernel/idreg-override.c            | 199 ++++++++++++++++++
 arch/arm64/kernel/kaslr.c                     |  44 +---
 arch/arm64/kernel/setup.c                     |  15 ++
 arch/arm64/kernel/sleep.S                     |   1 +
 arch/arm64/kvm/arm.c                          |   3 +
 arch/arm64/kvm/hyp/nvhe/hyp-init.S            |   2 +-
 arch/arm64/mm/mmu.c                           |   2 +-
 arch/arm64/mm/proc.S                          |  16 +-
 21 files changed, 505 insertions(+), 169 deletions(-)
 create mode 100644 arch/arm64/include/asm/setup.h
 create mode 100644 arch/arm64/kernel/idreg-override.c
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#1 lore raw

PATCH v3 1/21 arm64: Fix labels in el2_setup macros

If someone happens to write the following code:

	b	1f
	init_el2_state	vhe
1:
	[...]

they will be in for a long debugging session, as the label "1f" will be resolved *inside* the init_el2_state macro instead of after it. Not really what one expects.

Instead, rewite the EL2 setup macros to use unambiguous labels, thanks to the usual macro counter trick.

---
 arch/arm64/include/asm/el2_setup.h | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)
arch/arm64/include/asm/el2_setup.h +12 -12
index a7f5a1bbc8ac..540116de80bf 100644
@@ -45,24 +45,24 @@
 	mrs	x1, id_aa64dfr0_el1
 	sbfx	x0, x1, #ID_AA64DFR0_PMUVER_SHIFT, #4
 	cmp	x0, #1
-	b.lt	1f				// Skip if no PMU present
+	b.lt	.Lskip_pmu_\@			// Skip if no PMU present
 	mrs	x0, pmcr_el0			// Disable debug access traps
 	ubfx	x0, x0, #11, #5			// to EL2 and allow access to
-1:
+.Lskip_pmu_\@:
 	csel	x2, xzr, x0, lt			// all PMU counters from EL1
 
 	/* Statistical profiling */
 	ubfx	x0, x1, #ID_AA64DFR0_PMSVER_SHIFT, #4
-	cbz	x0, 3f				// Skip if SPE not present
+	cbz	x0, .Lskip_spe_\@		// Skip if SPE not present
 
 .ifeqs "\mode", "nvhe"
 	mrs_s	x0, SYS_PMBIDR_EL1              // If SPE available at EL2,
 	and	x0, x0, #(1 << SYS_PMBIDR_EL1_P_SHIFT)
-	cbnz	x0, 2f				// then permit sampling of physical
+	cbnz	x0, .Lskip_spe_el2_\@		// then permit sampling of physical
 	mov	x0, #(1 << SYS_PMSCR_EL2_PCT_SHIFT | \
 		      1 << SYS_PMSCR_EL2_PA_SHIFT)
 	msr_s	SYS_PMSCR_EL2, x0		// addresses and physical counter
-2:
+.Lskip_spe_el2_\@:
 	mov	x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
 	orr	x2, x2, x0			// If we don't have VHE, then
 						// use EL1&0 translation.
@@ -71,7 +71,7 @@
 						// and disable access from EL1
 .endif
 
-3:
+.Lskip_spe_\@:
 	msr	mdcr_el2, x2			// Configure debug traps
 .endm
 
@@ -79,9 +79,9 @@
 .macro __init_el2_lor
 	mrs	x1, id_aa64mmfr1_el1
 	ubfx	x0, x1, #ID_AA64MMFR1_LOR_SHIFT, 4
-	cbz	x0, 1f
+	cbz	x0, .Lskip_lor_\@
 	msr_s	SYS_LORC_EL1, xzr
-1:
+.Lskip_lor_\@:
 .endm
 
 /* Stage-2 translation */
@@ -93,7 +93,7 @@
 .macro __init_el2_gicv3
 	mrs	x0, id_aa64pfr0_el1
 	ubfx	x0, x0, #ID_AA64PFR0_GIC_SHIFT, #4
-	cbz	x0, 1f
+	cbz	x0, .Lskip_gicv3_\@
 
 	mrs_s	x0, SYS_ICC_SRE_EL2
 	orr	x0, x0, #ICC_SRE_EL2_SRE	// Set ICC_SRE_EL2.SRE==1
@@ -103,7 +103,7 @@
 	mrs_s	x0, SYS_ICC_SRE_EL2		// Read SRE back,
 	tbz	x0, #0, 1f			// and check that it sticks
 	msr_s	SYS_ICH_HCR_EL2, xzr		// Reset ICC_HCR_EL2 to defaults
-1:
+.Lskip_gicv3_\@:
 .endm
 
 .macro __init_el2_hstr
@@ -128,14 +128,14 @@
 .macro __init_el2_nvhe_sve
 	mrs	x1, id_aa64pfr0_el1
 	ubfx	x1, x1, #ID_AA64PFR0_SVE_SHIFT, #4
-	cbz	x1, 1f
+	cbz	x1, .Lskip_sve_\@
 
 	bic	x0, x0, #CPTR_EL2_TZ		// Also disable SVE traps
 	msr	cptr_el2, x0			// Disable copro. traps to EL2
 	isb
 	mov	x1, #ZCR_ELx_LEN_MASK		// SVE: Enable full vector
 	msr_s	SYS_ZCR_EL2, x1			// length for EL1.
-1:
+.Lskip_sve_\@:
 .endm
 
 .macro __init_el2_nvhe_prepare_eret
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#2 lore raw

PATCH v3 2/21 arm64: Fix outdated TCR setup comment

In reply to Marc Zyngier

The arm64 kernel has long be able to use more than 39bit VAs. Since day one, actually. Let's rewrite the offending comment.

---
 arch/arm64/mm/proc.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
arch/arm64/mm/proc.S +2 -2
index 1f7ee8c8b7b8..ece785477bdc 100644
@@ -464,8 +464,8 @@ SYM_FUNC_START(__cpu_setup)
 #endif
 	msr	mair_el1, x5
 	/*
-	 * Set/prepare TCR and TTBR. We use 512GB (39-bit) address range for
-	 * both user and kernel.
+	 * Set/prepare TCR and TTBR. TCR_EL1.T1SZ gets further
+	 * adjusted if the kernel is compiled with 52bit VA support.
 	 */
 	mov_q	x10, TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
 			TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
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#3 lore raw

PATCH v3 3/21 arm64: Turn the MMU-on sequence into a macro

In reply to Marc Zyngier

Turning the MMU on is a popular sport in the arm64 kernel, and we do it more than once, or even twice. As we are about to add even more, let's turn it into a macro.

No expected functional change.

---
 arch/arm64/include/asm/assembler.h | 17 +++++++++++++++++
 arch/arm64/kernel/head.S           | 19 ++++---------------
 arch/arm64/mm/proc.S               | 12 +-----------
 3 files changed, 22 insertions(+), 26 deletions(-)
arch/arm64/include/asm/assembler.h +17 -0
index bf125c591116..8cded93f99c3 100644
@@ -675,6 +675,23 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
 	.endif
 	.endm
 
+/*
+ * Set SCTLR_EL1 to the passed value, and invalidate the local icache
+ * in the process. This is called when setting the MMU on.
+ */
+.macro set_sctlr_el1, reg
+	msr	sctlr_el1, \reg
+	isb
+	/*
+	 * Invalidate the local I-cache so that any instructions fetched
+	 * speculatively from the PoC are discarded, since they may have
+	 * been dynamically patched at the PoU.
+	 */
+	ic	iallu
+	dsb	nsh
+	isb
+.endm
+
 /*
  * Check whether to yield to another runnable task from kernel mode NEON code
  * (which runs with preemption disabled).
arch/arm64/kernel/head.S +4 -15
index a0dc987724ed..28e9735302df 100644
@@ -703,16 +703,9 @@ SYM_FUNC_START(__enable_mmu)
 	offset_ttbr1 x1, x3
 	msr	ttbr1_el1, x1			// load TTBR1
 	isb
-	msr	sctlr_el1, x0
-	isb
-	/*
-	 * Invalidate the local I-cache so that any instructions fetched
-	 * speculatively from the PoC are discarded, since they may have
-	 * been dynamically patched at the PoU.
-	 */
-	ic	iallu
-	dsb	nsh
-	isb
+
+	set_sctlr_el1	x0
+
 	ret
 SYM_FUNC_END(__enable_mmu)
 
@@ -883,11 +876,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	tlbi	vmalle1				// Remove any stale TLB entries
 	dsb	nsh
 
-	msr	sctlr_el1, x19			// re-enable the MMU
-	isb
-	ic	iallu				// flush instructions fetched
-	dsb	nsh				// via old mapping
-	isb
+	set_sctlr_el1	x19			// re-enable the MMU
 
 	bl	__relocate_kernel
 #endif
arch/arm64/mm/proc.S +1 -11
index ece785477bdc..c967bfd30d2b 100644
@@ -291,17 +291,7 @@ skip_pgd:
 	/* We're done: fire up the MMU again */
 	mrs	x17, sctlr_el1
 	orr	x17, x17, #SCTLR_ELx_M
-	msr	sctlr_el1, x17
-	isb
-
-	/*
-	 * Invalidate the local I-cache so that any instructions fetched
-	 * speculatively from the PoC are discarded, since they may have
-	 * been dynamically patched at the PoU.
-	 */
-	ic	iallu
-	dsb	nsh
-	isb
+	set_sctlr_el1	x17
 
 	/* Set the flag to zero to indicate that we're all done */
 	str	wzr, [flag_ptr]
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#4 lore raw

PATCH v3 4/21 arm64: Provide an 'upgrade to VHE' stub hypercall

In reply to Marc Zyngier

As we are about to change the way a VHE system boots, let's provide the core helper, in the form of a stub hypercall that enables VHE and replicates the full EL1 context at EL2, thanks to EL1 and VHE-EL2 being extremely similar.

On exception return, the kernel carries on at EL2. Fancy!

Nothing calls this new hypercall yet, so no functional change.

---
 arch/arm64/include/asm/virt.h |  7 +++-
 arch/arm64/kernel/hyp-stub.S  | 67 +++++++++++++++++++++++++++++++++--
 2 files changed, 71 insertions(+), 3 deletions(-)
arch/arm64/include/asm/virt.h +6 -1
index ee6a48df89d9..7379f35ae2c6 100644
@@ -35,8 +35,13 @@
  */
 #define HVC_RESET_VECTORS 2
 
+/*
+ * HVC_VHE_RESTART - Upgrade the CPU from EL1 to EL2, if possible
+ */
+#define HVC_VHE_RESTART	3
+
 /* Max number of HYP stub hypercalls */
-#define HVC_STUB_HCALL_NR 3
+#define HVC_STUB_HCALL_NR 4
 
 /* Error returned when an invalid stub number is passed into x0 */
 #define HVC_STUB_ERR	0xbadca11
arch/arm64/kernel/hyp-stub.S +65 -2

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#5 lore raw

Re: [PATCH v3 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall

Quoted 8 lines · Marc Zyngier

As we are about to change the way a VHE system boots, let's provide the core helper, in the form of a stub hypercall that enables VHE and replicates the full EL1 context at EL2, thanks to EL1 and VHE-EL2 being extremely similar.

On exception return, the kernel carries on at EL2. Fancy!

Nothing calls this new hypercall yet, so no functional change.

Famous last words...

Quoted 42 lines
---
 arch/arm64/include/asm/virt.h |  7 +++-
 arch/arm64/kernel/hyp-stub.S  | 67 +++++++++++++++++++++++++++++++++--
 2 files changed, 71 insertions(+), 3 deletions(-)
arch/arm64/include/asm/virt.h +6 -1
index ee6a48df89d9..7379f35ae2c6 100644
@@ -35,8 +35,13 @@
  */
 #define HVC_RESET_VECTORS 2
 
+/*
+ * HVC_VHE_RESTART - Upgrade the CPU from EL1 to EL2, if possible
+ */
+#define HVC_VHE_RESTART	3
+
 /* Max number of HYP stub hypercalls */
-#define HVC_STUB_HCALL_NR 3
+#define HVC_STUB_HCALL_NR 4
 
 /* Error returned when an invalid stub number is passed into x0 */
 #define HVC_STUB_ERR	0xbadca11
arch/arm64/kernel/hyp-stub.S +1 -1
index 160f5881a0b7..0a84602344eb 100644
@@ -8,9 +8,9 @@
 
 #include <linux/init.h>
 #include <linux/linkage.h>
-#include <linux/irqchip/arm-gic-v3.h>
 
 #include <asm/assembler.h>
+#include <asm/el2_setup.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/ptrace.h>

arch/arm64/kernel/hyp-stub.S SYM_CODE_END(__hyp_stub_vectors) · line 55

Quoted 10 lines
arch/arm64/kernel/hyp-stub.S +3 -1
@@ -47,10 +47,13 @@ SYM_CODE_END(__hyp_stub_vectors)
 
 SYM_CODE_START_LOCAL(el1_sync)
 	cmp	x0, #HVC_SET_VECTORS
-	b.ne	2f
+	b.ne	1f
 	msr	vbar_el2, x1
 	b	9f
 
+1:	cmp	x0, #HVC_VHE_RESTART
+	b	mutate_to_vhe

And of course, I managed to send the *wrong* version of this patch. This should obviously be a "b.eq", otherwise none of the other hypercalls are reachable...

The correct version of this is now pushed in my tree[1].

Thanks,

        M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=hack/arm64-early-cpufeature

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#6 lore raw

PATCH v3 5/21 arm64: Initialise as nVHE before switching to VHE

In reply to Marc Zyngier

As we are aiming to be able to control whether we enable VHE or not, let's always drop down to EL1 first, and only then upgrade to VHE if at all possible.

This means that if the kernel is booted at EL2, we always start with a nVHE init, drop to EL1 to initialise the the kernel, and only then upgrade the kernel EL to EL2 if possible (the process is obviously shortened for secondary CPUs).

The resume path is handled similarly to a secondary CPU boot.

---
 arch/arm64/kernel/head.S     | 38 ++----------------------------------
 arch/arm64/kernel/hyp-stub.S | 24 +++++++++++++++++++++++
 arch/arm64/kernel/sleep.S    |  1 +
 3 files changed, 27 insertions(+), 36 deletions(-)
arch/arm64/kernel/head.S +2 -36
index 28e9735302df..07445fd976ef 100644
@@ -433,6 +433,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	bl	__pi_memset
 	dsb	ishst				// Make zero page visible to PTW
 
+	bl	switch_to_vhe
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
 #endif
@@ -493,42 +494,6 @@ SYM_INNER_LABEL(init_el1, SYM_L_LOCAL)
 	eret
 
 SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
-#ifdef CONFIG_ARM64_VHE
-	/*
-	 * Check for VHE being present. x2 being non-zero indicates that we
-	 * do have VHE, and that the kernel is intended to run at EL2.
-	 */
-	mrs	x2, id_aa64mmfr1_el1
-	ubfx	x2, x2, #ID_AA64MMFR1_VHE_SHIFT, #4
-#else
-	mov	x2, xzr
-#endif
-	cbz	x2, init_el2_nvhe
-
-	/*
-	 * When VHE _is_ in use, EL1 will not be used in the host and
-	 * requires no configuration, and all non-hyp-specific EL2 setup
-	 * will be done via the _EL1 system register aliases in __cpu_setup.
-	 */
-	mov_q	x0, HCR_HOST_VHE_FLAGS
-	msr	hcr_el2, x0
-	isb
-
-	init_el2_state vhe
-
-	isb
-
-	mov_q	x0, INIT_PSTATE_EL2
-	msr	spsr_el2, x0
-	msr	elr_el2, lr
-	mov	w0, #BOOT_CPU_MODE_EL2
-	eret
-
-SYM_INNER_LABEL(init_el2_nvhe, SYM_L_LOCAL)
-	/*
-	 * When VHE is not in use, early init of EL2 and EL1 needs to be
-	 * done here.
-	 */
 	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
 	msr	sctlr_el1, x0
 
@@ -623,6 +588,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	/*
 	 * Common entry point for secondary CPUs.
 	 */
+	bl	switch_to_vhe
 	bl	__cpu_secondary_check52bitva
 	bl	__cpu_setup			// initialise processor
 	adrp	x1, swapper_pg_dir
arch/arm64/kernel/hyp-stub.S +24 -0
index 0a84602344eb..8f5b735484c8 100644
@@ -181,3 +181,27 @@ SYM_FUNC_START(__hyp_reset_vectors)
 	hvc	#0
 	ret
 SYM_FUNC_END(__hyp_reset_vectors)
+
+/*
+ * Entry point to switch to VHE if deemed capable
+ */
+SYM_FUNC_START(switch_to_vhe)
+#ifdef CONFIG_ARM64_VHE
+	// Need to have booted at EL2
+	adr_l	x1, __boot_cpu_mode
+	ldr	w0, [x1]
+	cmp	w0, #BOOT_CPU_MODE_EL2
+	b.ne	1f
+
+	// and still be at EL1
+	mrs	x0, CurrentEL
+	cmp	x0, #CurrentEL_EL1
+	b.ne	1f
+
+	// Turn the world upside down
+	mov	x0, #HVC_VHE_RESTART
+	hvc	#0
+1:
+#endif
+	ret
+SYM_FUNC_END(switch_to_vhe)
arch/arm64/kernel/sleep.S +1 -0
index 6bdef7362c0e..5bfd9b87f85d 100644
@@ -100,6 +100,7 @@ SYM_FUNC_END(__cpu_suspend_enter)
 	.pushsection ".idmap.text", "awx"
 SYM_CODE_START(cpu_resume)
 	bl	init_kernel_el
+	bl	switch_to_vhe
 	bl	__cpu_setup
 	/* enable the MMU early - so we can access sleep_save_stash by va */
 	adrp	x1, swapper_pg_dir
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#7 lore raw

PATCH v3 6/21 arm64: Move VHE-specific SPE setup to mutate_to_vhe()

In reply to Marc Zyngier

There isn't much that a VHE kernel needs on top of whatever has been done for nVHE, so let's move the little we need to the VHE stub (the SPE setup), and drop the init_el2_state macro.

No expected functional change.

---
 arch/arm64/kernel/hyp-stub.S | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)
arch/arm64/kernel/hyp-stub.S +25 -3
index 8f5b735484c8..a3a23f3ef30d 100644
@@ -89,9 +89,6 @@ SYM_CODE_START_LOCAL(mutate_to_vhe)
 	msr	hcr_el2, x0
 	isb
 
-	// Doesn't do much on VHE, but still, worth a shot
-	init_el2_state vhe
-
 	// Use the EL1 allocated stack, per-cpu offset
 	mrs	x0, sp_el1
 	mov	sp, x0
@@ -104,6 +101,31 @@ SYM_CODE_START_LOCAL(mutate_to_vhe)
 	mrs_s	x0, SYS_VBAR_EL12
 	msr	vbar_el1, x0
 
+	// Fixup SPE configuration, if supported...
+	mrs	x1, id_aa64dfr0_el1
+	ubfx	x1, x1, #ID_AA64DFR0_PMSVER_SHIFT, #4
+	mov	x2, xzr
+	cbz	x1, skip_spe
+
+	// ... and not owned by EL3
+	mrs_s	x0, SYS_PMBIDR_EL1
+	and	x0, x0, #(1 << SYS_PMBIDR_EL1_P_SHIFT)
+	cbnz	x0, skip_spe
+
+	// Let the SPE driver in control of the sampling
+	mrs_s	x0, SYS_PMSCR_EL1
+	bic	x0, x0, #(1 << SYS_PMSCR_EL2_PCT_SHIFT)
+	bic	x0, x0, #(1 << SYS_PMSCR_EL2_PA_SHIFT)
+	msr_s	SYS_PMSCR_EL1, x0
+	mov	x2, #MDCR_EL2_TPMS
+
+skip_spe:
+	// For VHE, use EL2 translation and disable access from EL1
+	mrs	x0, mdcr_el2
+	bic	x0, x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
+	orr	x0, x0, x2
+	msr	mdcr_el2, x0
+
 	// Transfer the MM state from EL1 to EL2
 	mrs_s	x0, SYS_TCR_EL12
 	msr	tcr_el1, x0
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#8 lore raw

PATCH v3 7/21 arm64: Simplify init_el2_state to be non-VHE only

In reply to Marc Zyngier

As init_el2_state is now nVHE only, let's simplify it and drop the VHE setup.

---
 arch/arm64/include/asm/el2_setup.h | 36 +++++++-----------------------
 arch/arm64/kernel/head.S           |  2 +-
 arch/arm64/kvm/hyp/nvhe/hyp-init.S |  2 +-
 3 files changed, 10 insertions(+), 30 deletions(-)
arch/arm64/include/asm/el2_setup.h +8 -28
index 540116de80bf..d77d358f9395 100644
@@ -32,16 +32,14 @@
  * to transparently mess with the EL0 bits via CNTKCTL_EL1 access in
  * EL2.
  */
-.macro __init_el2_timers mode
-.ifeqs "\mode", "nvhe"
+.macro __init_el2_timers
 	mrs	x0, cnthctl_el2
 	orr	x0, x0, #3			// Enable EL1 physical timers
 	msr	cnthctl_el2, x0
-.endif
 	msr	cntvoff_el2, xzr		// Clear virtual offset
 .endm
 
-.macro __init_el2_debug mode
+.macro __init_el2_debug
 	mrs	x1, id_aa64dfr0_el1
 	sbfx	x0, x1, #ID_AA64DFR0_PMUVER_SHIFT, #4
 	cmp	x0, #1
@@ -55,7 +53,6 @@
 	ubfx	x0, x1, #ID_AA64DFR0_PMSVER_SHIFT, #4
 	cbz	x0, .Lskip_spe_\@		// Skip if SPE not present
 
-.ifeqs "\mode", "nvhe"
 	mrs_s	x0, SYS_PMBIDR_EL1              // If SPE available at EL2,
 	and	x0, x0, #(1 << SYS_PMBIDR_EL1_P_SHIFT)
 	cbnz	x0, .Lskip_spe_el2_\@		// then permit sampling of physical
@@ -66,10 +63,6 @@
 	mov	x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
 	orr	x2, x2, x0			// If we don't have VHE, then
 						// use EL1&0 translation.
-.else
-	orr	x2, x2, #MDCR_EL2_TPMS		// For VHE, use EL2 translation
-						// and disable access from EL1
-.endif
 
 .Lskip_spe_\@:
 	msr	mdcr_el2, x2			// Configure debug traps
@@ -145,37 +138,24 @@
 
 /**
  * Initialize EL2 registers to sane values. This should be called early on all
- * cores that were booted in EL2.
+ * cores that were booted in EL2. Note that everything gets initialised as
+ * if VHE was not evailable. The kernel context will be upgraded to VHE
+ * if possible later on in the boot process
  *
  * Regs: x0, x1 and x2 are clobbered.
  */
-.macro init_el2_state mode
-.ifnes "\mode", "vhe"
-.ifnes "\mode", "nvhe"
-.error "Invalid 'mode' argument"
-.endif
-.endif
-
+.macro init_el2_state
 	__init_el2_sctlr
-	__init_el2_timers \mode
-	__init_el2_debug \mode
+	__init_el2_timers
+	__init_el2_debug
 	__init_el2_lor
 	__init_el2_stage2
 	__init_el2_gicv3
 	__init_el2_hstr
-
-	/*
-	 * When VHE is not in use, early init of EL2 needs to be done here.
-	 * When VHE _is_ in use, EL1 will not be used in the host and
-	 * requires no configuration, and all non-hyp-specific EL2 setup
-	 * will be done via the _EL1 system register aliases in __cpu_setup.
-	 */
-.ifeqs "\mode", "nvhe"
 	__init_el2_nvhe_idregs
 	__init_el2_nvhe_cptr
 	__init_el2_nvhe_sve
 	__init_el2_nvhe_prepare_eret
-.endif
 .endm
 
 #endif /* __ARM_KVM_INIT_H__ */
arch/arm64/kernel/head.S +1 -1
index 07445fd976ef..36212c05df42 100644
@@ -501,7 +501,7 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 	msr	hcr_el2, x0
 	isb
 
-	init_el2_state nvhe
+	init_el2_state
 
 	/* Hypervisor stub */
 	adr_l	x0, __hyp_stub_vectors
arch/arm64/kvm/hyp/nvhe/hyp-init.S +1 -1
index 31b060a44045..222cfc3e7190 100644
@@ -189,7 +189,7 @@ SYM_CODE_START_LOCAL(__kvm_hyp_init_cpu)
 2:	msr	SPsel, #1			// We want to use SP_EL{1,2}
 
 	/* Initialize EL2 CPU state to sane values. */
-	init_el2_state nvhe			// Clobbers x0..x2
+	init_el2_state				// Clobbers x0..x2
 
 	/* Enable MMU, set vectors and stack. */
 	mov	x0, x28
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#9 lore raw

PATCH v3 8/21 arm64: Move SCTLR_EL1 initialisation to EL-agnostic code

In reply to Marc Zyngier

We can now move the initial SCTLR_EL1 setup to be used for both EL1 and EL2 setup.

---
 arch/arm64/kernel/head.S | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
arch/arm64/kernel/head.S +3 -5
index 36212c05df42..b425d2587cdb 100644
@@ -479,13 +479,14 @@ EXPORT_SYMBOL(kimage_vaddr)
  * booted in EL1 or EL2 respectively.
  */
 SYM_FUNC_START(init_kernel_el)
+	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	msr	sctlr_el1, x0
+
 	mrs	x0, CurrentEL
 	cmp	x0, #CurrentEL_EL2
 	b.eq	init_el2
 
 SYM_INNER_LABEL(init_el1, SYM_L_LOCAL)
-	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
-	msr	sctlr_el1, x0
 	isb
 	mov_q	x0, INIT_PSTATE_EL1
 	msr	spsr_el1, x0
@@ -494,9 +495,6 @@ SYM_INNER_LABEL(init_el1, SYM_L_LOCAL)
 	eret
 
 SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
-	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
-	msr	sctlr_el1, x0
-
 	mov_q	x0, HCR_HOST_NVHE_FLAGS
 	msr	hcr_el2, x0
 	isb
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#10 lore raw

PATCH v3 9/21 arm64: cpufeature: Add global feature override facility

In reply to Marc Zyngier

Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.

Nothing uses this yet, so we are pretty safe. For now.

---
 arch/arm64/include/asm/cpufeature.h |  2 ++
 arch/arm64/kernel/cpufeature.c      | 26 +++++++++++++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)
arch/arm64/include/asm/cpufeature.h +2 -0
index 9a555809b89c..465d2cb63bfc 100644
@@ -75,6 +75,8 @@ struct arm64_ftr_reg {
 	u64				sys_val;
 	u64				user_val;
 	const struct arm64_ftr_bits	*ftr_bits;
+	u64				*override_val;
+	u64				*override_mask;
 };
 
 extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
arch/arm64/kernel/cpufeature.c +21 -5
index e99eddec0a46..492321054bd5 100644
@@ -544,13 +544,17 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 	ARM64_FTR_END,
 };
 
-#define ARM64_FTR_REG(id, table) {		\
-	.sys_id = id,				\
-	.reg = 	&(struct arm64_ftr_reg){	\
-		.name = #id,			\
-		.ftr_bits = &((table)[0]),	\
+#define ARM64_FTR_REG_OVERRIDE(id, table, v, m) {		\
+		.sys_id = id,					\
+		.reg = 	&(struct arm64_ftr_reg){		\
+			.name = #id,				\
+			.ftr_bits = &((table)[0]),		\
+			.override_val = v,			\
+			.override_mask = m,			\
 	}}
 
+#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL)
+
 static const struct __ftr_reg_entry {
 	u32			sys_id;
 	struct arm64_ftr_reg 	*reg;
@@ -786,6 +790,18 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 
 	val &= valid_mask;
 
+	if (reg->override_mask && reg->override_val) {
+		u64 override = val;
+		override &= ~*reg->override_mask;
+		override |= (*reg->override_val & *reg->override_mask);
+
+		if (val != override)
+			pr_warn("%s: forced from %016llx to %016llx\n",
+				reg->name, val, override);
+
+		val = override;
+	}
+
 	reg->sys_val = val;
 	reg->strict_mask = strict_mask;
 	reg->user_mask = user_mask;
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#11 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Hi Marc,

Quoted 2 lines · Marc Zyngier

Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.

Yeah, it's dangerous. We can make it less so if we only allow safe values (e.g. lower if FTR_UNSIGNED).

arch/arm64/include/asm/cpufeature.h struct arm64_ftr_reg { · line 80

Quoted 11 lines
arch/arm64/include/asm/cpufeature.h +2 -0
index 9a555809b89c..465d2cb63bfc 100644
@@ -75,6 +75,8 @@ struct arm64_ftr_reg {
 	u64				sys_val;
 	u64				user_val;
 	const struct arm64_ftr_bits	*ftr_bits;
+	u64				*override_val;
+	u64				*override_mask;
 };

At the arm64_ftr_reg level, we don't have any information about the safe values for a feature. Could we instead move this to arm64_ftr_bits? We probably only need a single field. When populating the feature values, we can make sure it doesn't go above the hardware one.

I attempted a feature modification for MTE here, though I dropped the entire series in the meantime as we clarified the ARM ARM:

https://lore.kernel.org/linux-arm-kernel/[email protected]/

Srinivas copied it in his patch (but forgot to give credit ;)):

https://lore.kernel.org/linux-arm-msm/[email protected]/

The above adds a filter function but, instead, just use your mechanism in this series for idreg.feature setting via cmdline. The arm64_ftr_value() function extracts the hardware value and lowers it if a cmdline argument was passed.

Signature · 5 lines
Catalin
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#12 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Hi Catalin,

Quoted 8 lines · Catalin Marinas

Hi Marc,

Quoted 2 lines · Marc Zyngier

Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.

Yeah, it's dangerous. We can make it less so if we only allow safe values (e.g. lower if FTR_UNSIGNED).

My plan was also to allow non-safe values in order to trigger features that are not advertised by the HW. But I can understand if you are reluctant to allow such thing! :D

Quoted 22 lines

arch/arm64/include/asm/cpufeature.h struct arm64_ftr_reg { · line 80

Quoted 11 lines
arch/arm64/include/asm/cpufeature.h +2 -0
index 9a555809b89c..465d2cb63bfc 100644
@@ -75,6 +75,8 @@ struct arm64_ftr_reg {
 	u64				sys_val;
 	u64				user_val;
 	const struct arm64_ftr_bits	*ftr_bits;
+	u64				*override_val;
+	u64				*override_mask;
 };

At the arm64_ftr_reg level, we don't have any information about the safe values for a feature. Could we instead move this to arm64_ftr_bits? We probably only need a single field. When populating the feature values, we can make sure it doesn't go above the hardware one.

I attempted a feature modification for MTE here, though I dropped the entire series in the meantime as we clarified the ARM ARM:

https://lore.kernel.org/linux-arm-kernel/[email protected]/

Quoted 8 lines

Srinivas copied it in his patch (but forgot to give credit ;)):

https://lore.kernel.org/linux-arm-msm/[email protected]/

The above adds a filter function but, instead, just use your mechanism in this series for idreg.feature setting via cmdline. The arm64_ftr_value() function extracts the hardware value and lowers it if a cmdline argument was passed.

One thing is that it is not always possible to sanitise the value passed if it is required very early on, as I do with VHE. But in that case I actually check that we are VHE capable before starting to poke at VHE-specific state.

I came up with the following patch on top, which preserves the current global approach (no per arm64_ftr_bits state), but checks (and alters) the override as it iterates through the various fields.

For example, if I pass "arm64.nopauth kvm-arm.mode=nvhe id_aa64pfr1.bt=5" to the FVP, I get the following output:

[    0.000000] CPU features: SYS_ID_AA64ISAR1_EL1[31:28]: forced from 1 to 0
[    0.000000] CPU features: SYS_ID_AA64ISAR1_EL1[11:8]: forced from 1 to 0
[    0.000000] CPU features: SYS_ID_AA64MMFR1_EL1[11:8]: forced from 1 to 0
[    0.000000] CPU features: SYS_ID_AA64PFR1_EL1[3:0]: not forcing 1 to 5
[    0.000000] CPU features: detected: GIC system register CPU interface
[    0.000000] CPU features: detected: Hardware dirty bit management
[    0.000000] CPU features: detected: Spectre-v4
[    0.000000] CPU features: detected: Branch Target Identification

showing that the PAC features have been downgraded, together with VHE, but that BTI is still detected as value 5 was obviously bogus.

Thoughts?

        M.
arch/arm64/kernel/cpufeature.c +27 -12
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 	u64 strict_mask = ~0x0ULL;
 	u64 user_mask = 0;
 	u64 valid_mask = 0;
+	u64 override_val = 0, override_mask = 0;
 
 	const struct arm64_ftr_bits *ftrp;
 	struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 	if (!reg)
 		return;
 
+	if (reg->override_mask && reg->override_val) {
+		override_mask = *reg->override_mask;
+		override_val = *reg->override_val;
+	}
+
 	for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
 		u64 ftr_mask = arm64_ftr_mask(ftrp);
 		s64 ftr_new = arm64_ftr_value(ftrp, new);
+		s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+		if ((ftr_mask & override_mask) == ftr_mask) {
+			if (ftr_ovr < ftr_new) {
+				pr_warn("%s[%d:%d]: forced from %llx to %llx\n",
+					reg->name,
+					ftrp->shift + ftrp->width - 1,
+					ftrp->shift, ftr_new, ftr_ovr);
+
+				ftr_new = ftr_ovr;
+			} else if (ftr_ovr != ftr_new) {
+				pr_warn("%s[%d:%d]: not forcing %llx to %llx\n",
+					reg->name,
+					ftrp->shift + ftrp->width - 1,
+					ftrp->shift, ftr_new, ftr_ovr);
+
+				/* Remove the override */
+				*reg->override_mask &= ~ftr_mask;
+				*reg->override_val &= ~ftr_mask;
+			}
+		}
 
 		val = arm64_ftr_set_value(ftrp, val, ftr_new);
 
@@ -800,18 +827,6 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 
 	val &= valid_mask;
 
-	if (reg->override_mask && reg->override_val) {
-		u64 override = val;
-		override &= ~*reg->override_mask;
-		override |= (*reg->override_val & *reg->override_mask);
-
-		if (val != override)
-			pr_warn("%s: forced from %016llx to %016llx\n",
-				reg->name, val, override);
-
-		val = override;
-	}
-
 	reg->sys_val = val;
 	reg->strict_mask = strict_mask;
 	reg->user_mask = user_mask;
Signature · 5 lines
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#13 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Hi Marc,

Quoted 93 lines · Marc Zyngier

Hi Catalin,

Quoted 8 lines · Catalin Marinas

Hi Marc,

Quoted 2 lines · Marc Zyngier

Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.

Yeah, it's dangerous. We can make it less so if we only allow safe values (e.g. lower if FTR_UNSIGNED).

My plan was also to allow non-safe values in order to trigger features that are not advertised by the HW. But I can understand if you are reluctant to allow such thing! :D

Quoted 22 lines

arch/arm64/include/asm/cpufeature.h struct arm64_ftr_reg { · line 80

Quoted 11 lines
arch/arm64/include/asm/cpufeature.h +2 -0
index 9a555809b89c..465d2cb63bfc 100644
@@ -75,6 +75,8 @@ struct arm64_ftr_reg {
      u64                sys_val;
      u64                user_val;
      const struct arm64_ftr_bits    *ftr_bits;
+    u64                *override_val;
+    u64                *override_mask;
  };

At the arm64_ftr_reg level, we don't have any information about the safe values for a feature. Could we instead move this to arm64_ftr_bits? We probably only need a single field. When populating the feature values, we can make sure it doesn't go above the hardware one.

I attempted a feature modification for MTE here, though I dropped the entire series in the meantime as we clarified the ARM ARM:

https://lore.kernel.org/linux-arm-kernel/[email protected]/

Quoted 8 lines

Srinivas copied it in his patch (but forgot to give credit ;)):

https://lore.kernel.org/linux-arm-msm/[email protected]/

The above adds a filter function but, instead, just use your mechanism in this series for idreg.feature setting via cmdline. The arm64_ftr_value() function extracts the hardware value and lowers it if a cmdline argument was passed.

One thing is that it is not always possible to sanitise the value passed if it is required very early on, as I do with VHE. But in that case I actually check that we are VHE capable before starting to poke at VHE-specific state.

I came up with the following patch on top, which preserves the current global approach (no per arm64_ftr_bits state), but checks (and alters) the override as it iterates through the various fields.

For example, if I pass "arm64.nopauth kvm-arm.mode=nvhe id_aa64pfr1.bt=5" to the FVP, I get the following output:

[    0.000000] CPU features: SYS_ID_AA64ISAR1_EL1[31:28]: forced from 1 to 0 [    0.000000] CPU features: SYS_ID_AA64ISAR1_EL1[11:8]: forced from 1 to 0 [    0.000000] CPU features: SYS_ID_AA64MMFR1_EL1[11:8]: forced from 1 to 0 [    0.000000] CPU features: SYS_ID_AA64PFR1_EL1[3:0]: not forcing 1 to 5 [    0.000000] CPU features: detected: GIC system register CPU interface [    0.000000] CPU features: detected: Hardware dirty bit management [    0.000000] CPU features: detected: Spectre-v4
[    0.000000] CPU features: detected: Branch Target Identification

showing that the PAC features have been downgraded, together with VHE, but that BTI is still detected as value 5 was obviously bogus.

Thoughts?

        M.

arch/arm64/kernel/cpufeature.c +3 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
      u64 strict_mask = ~0x0ULL;
      u64 user_mask = 0;
      u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
      const struct arm64_ftr_bits *ftrp;
      struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
      if (!reg)
          return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) · line 796

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
      for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
          u64 ftr_mask = arm64_ftr_mask(ftrp);
          s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

i.e,

	ftr_val = arm64_ftr_safe_value(ftrp, ftr_ovr, ftr_new);

Suzuki
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#14 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Hi Suzuki,

Quoted 3 lines · Suzuki K Poulose

Hi Marc,

On 1/11/21 7:48 PM, Marc Zyngier wrote:

[...]

Quoted 31 lines
Quoted 20 lines
arch/arm64/kernel/cpufeature.c +1 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, 
 u64 new)
      u64 strict_mask = ~0x0ULL;
      u64 user_mask = 0;
      u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
      const struct arm64_ftr_bits *ftrp;

     struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);

arch/arm64/kernel/cpufeature.c +2 -0
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, 
 u64 new)
      if (!reg)
          return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 sys_reg, · line 797

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
      for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
          u64 ftr_mask = arm64_ftr_mask(ftrp);
          s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {
Quoted 8 lines

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

I like the idea of using the helper, as it cleanups up the code a bit. However, not being to set a feature to a certain value could be restrictive, as in general, it means that we can only disable a feature and not adjust its level of support.

Take PMUVER for example: with the helper, I can't override it from v8.4 to v8.1. I can only go to v8.0.

Is it something we care about?

Thanks,

        M.
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#15 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Quoted 49 lines · Marc Zyngier

Hi Suzuki,

Quoted 3 lines · Suzuki K Poulose

Hi Marc,

On 1/11/21 7:48 PM, Marc Zyngier wrote:

[...]

Quoted 31 lines
Quoted 20 lines
arch/arm64/kernel/cpufeature.c +1 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, 
 u64 new)
      u64 strict_mask = ~0x0ULL;
      u64 user_mask = 0;
      u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
      const struct arm64_ftr_bits *ftrp;

     struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);

arch/arm64/kernel/cpufeature.c +2 -0
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, 
 u64 new)
      if (!reg)
          return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 sys_reg, · line 797

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
      for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
          u64 ftr_mask = arm64_ftr_mask(ftrp);
          s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {
Quoted 8 lines

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

Quoted 7 lines

I like the idea of using the helper, as it cleanups up the code a bit. However, not being to set a feature to a certain value could be restrictive, as in general, it means that we can only disable a feature and not adjust its level of support.

Take PMUVER for example: with the helper, I can't override it from v8.4 to v8.1. I can only go to v8.0.

Actually, we can only *disable* the PMU altogether. Same question though...

        M.
Quoted 6 lines

Is it something we care about?

Thanks,

        M.
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#16 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Quoted 53 lines · Marc Zyngier
Quoted 52 lines · Marc Zyngier

Hi Suzuki,

Quoted 3 lines · Suzuki K Poulose

Hi Marc,

On 1/11/21 7:48 PM, Marc Zyngier wrote:

[...]

Quoted 29 lines
Quoted 18 lines
arch/arm64/kernel/cpufeature.c +3 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
       u64 strict_mask = ~0x0ULL;
       u64 user_mask = 0;
       u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
       const struct arm64_ftr_bits *ftrp;
       struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
       if (!reg)
           return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) · line 796

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
       for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
           u64 ftr_mask = arm64_ftr_mask(ftrp);
           s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {
Quoted 8 lines

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

I like the idea of using the helper, as it cleanups up the code a bit. However, not being to set a feature to a certain value could be restrictive, as in general, it means that we can only disable a feature and not adjust its level of support.

Quoted 4 lines
Quoted 2 lines

Take PMUVER for example: with the helper, I can't override it from v8.4 to v8.1. I can only go to v8.0.

Actually, we can only *disable* the PMU altogether. Same question though...

It depends on two things :

1) What is the safe value for an EXACT typed feature ? Usually, that means either disabled, or the lowest possible value.

2) How is this value consumed ?
a) i.e, Do we use the per-CPU value
Then none of these changes have any effect
b) System wide value ?
Then we get the safe value as "influenced" by the infrastructure.

The safe value we use for EXACT features is exclusively for making sure that the system uses the safe assumption and thus should be the best option.

To answer your question, for PMU, it is 0, implies, v8.0. Or we could update the safe value to -1 (0xf) as the safe value, which is a bit more safer, kind of implying that the PMU is not a standard one.

Cheers
Suzuki

Quoted 10 lines

        M.

Quoted 6 lines

Is it something we care about?

Thanks,

        M.

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#17 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

In reply to Marc Zyngier
Quoted 47 lines · Marc Zyngier

Hi Suzuki,

Quoted 3 lines · Suzuki K Poulose

Hi Marc,

On 1/11/21 7:48 PM, Marc Zyngier wrote:

[...]

Quoted 29 lines
Quoted 18 lines
arch/arm64/kernel/cpufeature.c +3 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
       u64 strict_mask = ~0x0ULL;
       u64 user_mask = 0;
       u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
       const struct arm64_ftr_bits *ftrp;
       struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
       if (!reg)
           return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) · line 796

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
       for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
           u64 ftr_mask = arm64_ftr_mask(ftrp);
           s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {
Quoted 8 lines

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

Quoted 7 lines

I like the idea of using the helper, as it cleanups up the code a bit. However, not being to set a feature to a certain value could be restrictive, as in general, it means that we can only disable a feature and not adjust its level of support.

Take PMUVER for example: with the helper, I can't override it from v8.4 to v8.1. I can only go to v8.0.

My point is, we set this only for the "init" of cpu features. So, even if we init to a custom , non-(default-safe) value, the secondary CPUs could scream, and the system wide safe value could fall back to the "safe" value for EXACT features, no matter what you did to init it.

Also, it will be dangerous for things like PAC, as the lower level value may not be compatible with the "actual" cpu feature supported.

So simply setting to a lower value for EXACT features is generally not safe, though I understand some are exceptions.

Suzuki

Quoted 6 lines

Is it something we care about?

Thanks,

        M.

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#18 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

Quoted 55 lines · Suzuki K Poulose
Quoted 54 lines · Marc Zyngier

Hi Suzuki,

Quoted 3 lines · Suzuki K Poulose

Hi Marc,

On 1/11/21 7:48 PM, Marc Zyngier wrote:

[...]

Quoted 31 lines
Quoted 20 lines
arch/arm64/kernel/cpufeature.c +1 -0
index 894af60b9669..00d99e593b65 100644
@@ -774,6 +774,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, 
 u64 new)
       u64 strict_mask = ~0x0ULL;
       u64 user_mask = 0;
       u64 valid_mask = 0;
+    u64 override_val = 0, override_mask = 0;
 
       const struct arm64_ftr_bits *ftrp;

      struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);

arch/arm64/kernel/cpufeature.c +2 -0
@@ -781,9 +782,35 @@ static void __init init_cpu_ftr_reg(u32 
 sys_reg, u64 new)
       if (!reg)
           return;
 
+    if (reg->override_mask && reg->override_val) {
+        override_mask = *reg->override_mask;

arch/arm64/kernel/cpufeature.c static void __init init_cpu_ftr_reg(u32 · line 797

Quoted 10 lines
arch/arm64/kernel/cpufeature.c +7 -0
+        override_val = *reg->override_val;
+    }
+
       for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
           u64 ftr_mask = arm64_ftr_mask(ftrp);
           s64 ftr_new = arm64_ftr_value(ftrp, new);
+        s64 ftr_ovr = arm64_ftr_value(ftrp, override_val);
+
+        if ((ftr_mask & override_mask) == ftr_mask) {
+            if (ftr_ovr < ftr_new) {
Quoted 8 lines

Here we assume that all the features are FTR_LOWER_SAFE. We could probably use arm64_ftr_safe_value(ftrp, ftr_new, ftr_ovr) here ? That would cover us for both HIGHER_SAFE and LOWER_SAFE features. However that may be restrictive for FTR_EXACT, as we the safe value would be set to "ftr->safe_val". I guess that may be better than forcing to use an unsafe value for the boot CPU, which could anyway conflict with the other CPUs and eventually trigger the ftr alue to be safe_val.

I like the idea of using the helper, as it cleanups up the code a bit. However, not being to set a feature to a certain value could be restrictive, as in general, it means that we can only disable a feature and not adjust its level of support.

Quoted 7 lines
Quoted 2 lines

Take PMUVER for example: with the helper, I can't override it from v8.4 to v8.1. I can only go to v8.0.

My point is, we set this only for the "init" of cpu features. So, even if we init to a custom , non-(default-safe) value, the secondary CPUs could scream, and the system wide safe value could fall back to the "safe" value for EXACT features, no matter what you did to init it.

Right. So let's go with the safe value for EXACT features for now, and let the override fail if that's not what the user asked for.

After all, there are only so many things we want to support as an override, and in all the cases at hand, using the safe value actually matches what we want to do.

We can always revisit this if and when we need a different behaviour.

Thanks,

        M.
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#19 lore raw

Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility

In reply to Catalin Marinas

Hi Catalin,

Quoted 24 lines · Catalin Marinas

Hi Marc,

Quoted 2 lines · Marc Zyngier

Add a facility to globally override a feature, no matter what the HW says. Yes, this is dangerous.

Yeah, it's dangerous. We can make it less so if we only allow safe values (e.g. lower if FTR_UNSIGNED).

arch/arm64/include/asm/cpufeature.h struct arm64_ftr_reg { · line 80

Quoted 11 lines
arch/arm64/include/asm/cpufeature.h +2 -0
index 9a555809b89c..465d2cb63bfc 100644
@@ -75,6 +75,8 @@ struct arm64_ftr_reg {
  	u64				sys_val;
  	u64				user_val;
  	const struct arm64_ftr_bits	*ftr_bits;
+	u64				*override_val;
+	u64				*override_mask;
  };

At the arm64_ftr_reg level, we don't have any information about the safe values for a feature. Could we instead move this to arm64_ftr_bits? We probably only need a single field. When populating the feature values, we can make sure it doesn't go above the hardware one.

Quoted 6 lines

I attempted a feature modification for MTE here, though I dropped the entire series in the meantime as we clarified the ARM ARM:

https://lore.kernel.org/linux-arm-kernel/[email protected]/

Srinivas copied it in his patch (but forgot to give credit ;)):

Sorry about that. I did mention that its taken from your patch-set in my cover letter. But missed your signed-off-by in the patch.

https://lore.kernel.org/linux-arm-msm/[email protected]/T/#m1ae76e6096c07ab5f1636a4e383a3fd6cfb4665f

Since we can ignore my patch with the mechanism added by Marc, I am not re-sending this. Thanks.

Quoted 8 lines

https://lore.kernel.org/linux-arm-msm/[email protected]/

The above adds a filter function but, instead, just use your mechanism in this series for idreg.feature setting via cmdline. The arm64_ftr_value() function extracts the hardware value and lowers it if a cmdline argument was passed.

author maintainer
#20 lore raw

PATCH v3 10/21 arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding()

In reply to Marc Zyngier

__read_sysreg_by_encoding() is used by a bunch of cpufeature helpers, which should take the feature override into account. Let's do that.

For a good measure (and because we are likely to need to further down the line), make this helper available to the rest of the non-modular kernel.

Code that needs to know the *real* features of a CPU can still use read_sysreg_s(), and find the bare, ugly truth.

---
 arch/arm64/include/asm/cpufeature.h |  1 +
 arch/arm64/kernel/cpufeature.c      | 15 +++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)
arch/arm64/include/asm/cpufeature.h +1 -0
index 465d2cb63bfc..fe0130d6c0ff 100644
@@ -602,6 +602,7 @@ void __init setup_cpu_features(void);
 void check_local_cpu_capabilities(void);
 
 u64 read_sanitised_ftr_reg(u32 id);
+u64 __read_sysreg_by_encoding(u32 sys_id);
 
 static inline bool cpu_supports_mixed_endian_el0(void)
 {
arch/arm64/kernel/cpufeature.c +13 -2
index 492321054bd5..1cc93a2324dc 100644
@@ -1131,14 +1131,17 @@ u64 read_sanitised_ftr_reg(u32 id)
 EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg);
 
 #define read_sysreg_case(r)	\
-	case r:		return read_sysreg_s(r)
+	case r:		val = read_sysreg_s(r); break;
 
 /*
  * __read_sysreg_by_encoding() - Used by a STARTING cpu before cpuinfo is populated.
  * Read the system register on the current CPU
  */
-static u64 __read_sysreg_by_encoding(u32 sys_id)
+u64 __read_sysreg_by_encoding(u32 sys_id)
 {
+	struct arm64_ftr_reg *regp;
+	u64 val;
+
 	switch (sys_id) {
 	read_sysreg_case(SYS_ID_PFR0_EL1);
 	read_sysreg_case(SYS_ID_PFR1_EL1);
@@ -1181,6 +1184,14 @@ static u64 __read_sysreg_by_encoding(u32 sys_id)
 		BUG();
 		return 0;
 	}
+
+	regp  = get_arm64_ftr_reg(sys_id);
+	if (regp && regp->override_mask && regp->override_val) {
+		val &= ~*regp->override_mask;
+		val |= (*regp->override_val & *regp->override_mask);
+	}
+
+	return val;
 }
 
 #include <linux/irqchip/arm-gic-v3.h>
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#21 lore raw

PATCH v3 11/21 arm64: Extract early FDT mapping from kaslr_early_init()

In reply to Marc Zyngier

As we want to parse more options very early in the kernel lifetime, let's always map the FDT early. This is achieved by moving that code out of kaslr_early_init().

No functionnal change expected.

---
 arch/arm64/include/asm/setup.h | 11 +++++++++++
 arch/arm64/kernel/head.S       |  3 ++-
 arch/arm64/kernel/kaslr.c      |  7 +++----
 arch/arm64/kernel/setup.c      | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/setup.h
arch/arm64/include/asm/setup.h new file +11 -0
new file mode 100644
index 000000000000..d3320618ed14
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __ARM64_ASM_SETUP_H
+#define __ARM64_ASM_SETUP_H
+
+#include <uapi/asm/setup.h>
+
+void *get_early_fdt_ptr(void);
+void early_fdt_map(u64 dt_phys);
+
+#endif
arch/arm64/kernel/head.S +2 -1
index b425d2587cdb..d74e5f84042e 100644
@@ -433,6 +433,8 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	bl	__pi_memset
 	dsb	ishst				// Make zero page visible to PTW
 
+	mov	x0, x21				// pass FDT address in x0
+	bl	early_fdt_map			// Try mapping the FDT early
 	bl	switch_to_vhe
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
@@ -440,7 +442,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 #ifdef CONFIG_RANDOMIZE_BASE
 	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
 	b.ne	0f
-	mov	x0, x21				// pass FDT address in x0
 	bl	kaslr_early_init		// parse FDT for KASLR options
 	cbz	x0, 0f				// KASLR disabled? just proceed
 	orr	x23, x23, x0			// record KASLR offset
arch/arm64/kernel/kaslr.c +3 -4
index 1c74c45b9494..5fc86e7d01a1 100644
@@ -19,6 +19,7 @@
 #include <asm/memory.h>
 #include <asm/mmu.h>
 #include <asm/sections.h>
+#include <asm/setup.h>
 
 enum kaslr_status {
 	KASLR_ENABLED,
@@ -92,12 +93,11 @@ static __init bool is_kaslr_disabled_cmdline(void *fdt)
  * containing function pointers) to be reinitialized, and zero-initialized
  * .bss variables will be reset to 0.
  */
-u64 __init kaslr_early_init(u64 dt_phys)
+u64 __init kaslr_early_init(void)
 {
 	void *fdt;
 	u64 seed, offset, mask, module_range;
 	unsigned long raw;
-	int size;
 
 	/*
 	 * Set a reasonable default for module_alloc_base in case
@@ -111,8 +111,7 @@ u64 __init kaslr_early_init(u64 dt_phys)
 	 * and proceed with KASLR disabled. We will make another
 	 * attempt at mapping the FDT in setup_machine()
 	 */
-	early_fixmap_init();
-	fdt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
+	fdt = get_early_fdt_ptr();
 	if (!fdt) {
 		kaslr_status = KASLR_DISABLED_FDT_REMAP;
 		return 0;
arch/arm64/kernel/setup.c +15 -0
index c18aacde8bb0..01a994730754 100644
@@ -168,6 +168,21 @@ static void __init smp_build_mpidr_hash(void)
 		pr_warn("Large number of MPIDR hash buckets detected\n");
 }
 
+static void *early_fdt_ptr __initdata;
+
+void __init *get_early_fdt_ptr(void)
+{
+	return early_fdt_ptr;
+}
+
+void __init early_fdt_map(u64 dt_phys)
+{
+	int fdt_size;
+
+	early_fixmap_init();
+	early_fdt_ptr = fixmap_remap_fdt(dt_phys, &fdt_size, PAGE_KERNEL);
+}
+
 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
 	int size;
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#22 lore raw

PATCH v3 12/21 arm64: cpufeature: Add an early command-line cpufeature override facility

In reply to Marc Zyngier

In order to be able to override CPU features at boot time, let's add a command line parser that matches options of the form "cpureg.feature=value", and store the corresponding value into the override val/mask pair.

No features are currently defined, so no expected change in functionality.

---
 arch/arm64/kernel/Makefile         |   2 +-
 arch/arm64/kernel/head.S           |   1 +
 arch/arm64/kernel/idreg-override.c | 119 +++++++++++++++++++++++++++++
 3 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kernel/idreg-override.c
arch/arm64/kernel/Makefile +1 -1
index 86364ab6f13f..2262f0392857 100644
@@ -17,7 +17,7 @@ obj-y			:= debug-monitors.o entry.o irq.o fpsimd.o		\
 			   return_address.o cpuinfo.o cpu_errata.o		\
 			   cpufeature.o alternative.o cacheinfo.o		\
 			   smp.o smp_spin_table.o topology.o smccc-call.o	\
-			   syscall.o proton-pack.o
+			   syscall.o proton-pack.o idreg-override.o
 
 targets			+= efi-entry.o
 
arch/arm64/kernel/head.S +1 -0
index d74e5f84042e..b3c4dd04f74b 100644
@@ -435,6 +435,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 
 	mov	x0, x21				// pass FDT address in x0
 	bl	early_fdt_map			// Try mapping the FDT early
+	bl	init_shadow_regs
 	bl	switch_to_vhe
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
arch/arm64/kernel/idreg-override.c new file +119 -0

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#23 lore raw

PATCH v3 13/21 arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line

In reply to Marc Zyngier

As we want to be able to disable VHE at runtime, let's match "id_aa64mmfr1.vh=" from the command line as an override. This doesn't have much effect yet as our boot code doesn't look at the cpufeature, but only at the HW registers.

---
 arch/arm64/include/asm/cpufeature.h |  3 +++
 arch/arm64/kernel/cpufeature.c      |  6 +++++-
 arch/arm64/kernel/idreg-override.c  | 12 ++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)
arch/arm64/include/asm/cpufeature.h +3 -0
index fe0130d6c0ff..80a5f423444e 100644
@@ -814,6 +814,9 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
 	return 8;
 }
 
+extern u64 id_aa64mmfr1_val;
+extern u64 id_aa64mmfr1_mask;
+
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);
 
arch/arm64/kernel/cpufeature.c +5 -1
index 1cc93a2324dc..cc435b3dcd53 100644
@@ -555,6 +555,9 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 
 #define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL)
 
+u64 id_aa64mmfr1_val;
+u64 id_aa64mmfr1_mask;
+
 static const struct __ftr_reg_entry {
 	u32			sys_id;
 	struct arm64_ftr_reg 	*reg;
@@ -602,7 +605,8 @@ static const struct __ftr_reg_entry {
 
 	/* Op1 = 0, CRn = 0, CRm = 7 */
 	ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
-	ARM64_FTR_REG(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1),
+	ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1,
+			       &id_aa64mmfr1_val, &id_aa64mmfr1_mask),
 	ARM64_FTR_REG(SYS_ID_AA64MMFR2_EL1, ftr_id_aa64mmfr2),
 
 	/* Op1 = 0, CRn = 1, CRm = 2 */
arch/arm64/kernel/idreg-override.c +12 -0
index 392f93b67103..75d9845f489b 100644
@@ -10,6 +10,7 @@
 #include <linux/libfdt.h>
 
 #include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
 #include <asm/setup.h>
 
 struct reg_desc {
@@ -22,7 +23,18 @@ struct reg_desc {
 	} 			fields[];
 };
 
+static const struct reg_desc mmfr1 __initdata = {
+	.name		= "id_aa64mmfr1",
+	.val		= &id_aa64mmfr1_val,
+	.mask		= &id_aa64mmfr1_mask,
+	.fields		= {
+	        { "vh", ID_AA64MMFR1_VHE_SHIFT },
+		{}
+	},
+};
+
 static const struct reg_desc * const regs[] __initdata = {
+	&mmfr1,
 };
 
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
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#24 lore raw

PATCH v3 14/21 arm64: Honor VHE being disabled from the command-line

In reply to Marc Zyngier

Finally we can check whether VHE is disabled on the command line, and not enable it if that's the user's wish.

---
 arch/arm64/kernel/hyp-stub.S | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)
arch/arm64/kernel/hyp-stub.S +14 -3
index a3a23f3ef30d..5912ee57a877 100644
@@ -77,13 +77,24 @@ SYM_CODE_END(el1_sync)
 SYM_CODE_START_LOCAL(mutate_to_vhe)
 	// Sanity check: MMU *must* be off
 	mrs	x0, sctlr_el2
-	tbnz	x0, #0, 1f
+	tbnz	x0, #0, 2f
 
 	// Needs to be VHE capable, obviously
 	mrs	x0, id_aa64mmfr1_el1
 	ubfx	x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4
-	cbz	x0, 1f
+	cbz	x0, 2f
 
+	// Check whether VHE is disabled from the command line
+	adr_l	x1, id_aa64mmfr1_val
+	ldr	x0, [x1]
+	adr_l	x1, id_aa64mmfr1_mask
+	ldr	x1, [x1]
+	ubfx	x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4
+	ubfx	x1, x1, #ID_AA64MMFR1_VHE_SHIFT, #4
+	cbz	x1, 1f
+	and	x0, x0, x1
+	cbz	x0, 2f
+1:
 	// Engage the VHE magic!
 	mov_q	x0, HCR_HOST_VHE_FLAGS
 	msr	hcr_el2, x0
@@ -152,7 +163,7 @@ skip_spe:
 	orr	x0, x0, x1
 	msr	spsr_el1, x0
 
-1:	eret
+2:	eret
 SYM_CODE_END(mutate_to_vhe)
 
 .macro invalid_vector	label
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#25 lore raw

PATCH v3 15/21 arm64: Add an aliasing facility for the idreg override

In reply to Marc Zyngier

In order to map the override of idregs to options that a user can easily understand, let's introduce yet another option array, which maps an option to the corresponding idreg options.

---
 arch/arm64/kernel/idreg-override.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
arch/arm64/kernel/idreg-override.c +20 -0
index 75d9845f489b..16bc8b3b93ae 100644
@@ -37,6 +37,12 @@ static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
 };
 
+static const struct {
+	const char * const	alias;
+	const char * const	feature;
+} aliases[] __initdata = {
+};
+
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
 			     int f, u64 *v)
 {
@@ -80,6 +86,18 @@ static void __init match_options(const char *cmdline)
 	}
 }
 
+static __init void match_aliases(const char *cmdline)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(aliases); i++) {
+		char *str = strstr(cmdline, aliases[i].alias);
+
+		if ((str == cmdline || (str > cmdline && *(str - 1) == ' ')))
+			match_options(aliases[i].feature);
+	}
+}
+
 static __init void parse_cmdline(void)
 {
 	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
@@ -100,6 +118,7 @@ static __init void parse_cmdline(void)
 			goto out;
 
 		match_options(prop);
+		match_aliases(prop);
 
 		if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
 			return;
@@ -107,6 +126,7 @@ static __init void parse_cmdline(void)
 
 out:
 	match_options(CONFIG_CMDLINE);
+	match_aliases(CONFIG_CMDLINE);
 }
 
 void __init init_shadow_regs(void)
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#26 lore raw

PATCH v3 16/21 arm64: Make kvm-arm.mode={nvhe,protected} an alias of id_aa64mmfr1.vh=0

In reply to Marc Zyngier

Admitedly, passing id_aa64mmfr1.vh=0 on the command-line isn't that easy to understand, and it is likely that users would much prefer write "kvm-arm.mode=nvhe", or "...=protected".

So here you go. This has the added advantage that we can now always honor the "kvm-arm.mode=protected" option, even when booting on a VHE system.

---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/arm64/kernel/idreg-override.c              | 2 ++
 arch/arm64/kvm/arm.c                            | 3 +++
 3 files changed, 8 insertions(+)
Documentation/admin-guide/kernel-parameters.txt +3 -0
index 9e3cdb271d06..2786fd39a047 100644
@@ -2257,6 +2257,9 @@
 	kvm-arm.mode=
 			[KVM,ARM] Select one of KVM/arm64's modes of operation.
 
+			nvhe: Standard nVHE-based mode, without support for
+			      protected guests.
+
 			protected: nVHE-based mode with support for guests whose
 				   state is kept private from the host.
 				   Not valid if the kernel is running in EL2.
arch/arm64/kernel/idreg-override.c +2 -0
index 16bc8b3b93ae..1db54878b2c4 100644
@@ -41,6 +41,8 @@ static const struct {
 	const char * const	alias;
 	const char * const	feature;
 } aliases[] __initdata = {
+	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
+	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
 };
 
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
arch/arm64/kvm/arm.c +3 -0
index 04c44853b103..597565a65ca2 100644
@@ -1966,6 +1966,9 @@ static int __init early_kvm_mode_cfg(char *arg)
 		return 0;
 	}
 
+	if (strcmp(arg, "nvhe") == 0 && !WARN_ON(is_kernel_in_hyp_mode()))
+		return 0;
+
 	return -EINVAL;
 }
 early_param("kvm-arm.mode", early_kvm_mode_cfg);
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#27 lore raw

PATCH v3 17/21 KVM: arm64: Document HVC_VHE_RESTART stub hypercall

In reply to Marc Zyngier

For completeness, let's document the HVC_VHE_RESTART stub.

---
 Documentation/virt/kvm/arm/hyp-abi.rst | 9 +++++++++
 1 file changed, 9 insertions(+)
Documentation/virt/kvm/arm/hyp-abi.rst +9 -0
index 83cadd8186fa..1ba628baf11b 100644
@@ -58,6 +58,15 @@ these functions (see arch/arm{,64}/include/asm/virt.h):
   into place (arm64 only), and jump to the restart address while at HYP/EL2.
   This hypercall is not expected to return to its caller.
 
+* ::
+
+    x0 = HVC_VHE_RESTART (arm64 only)
+
+  Attempt to upgrade the kernel's exception level from EL1 to EL2 by enabling
+  the VHE mode. This is conditioned by the CPU supporting VHE, the EL2 MMU
+  being off, and VHE not being disabled by any other mean (comment line option,
+  for example).
+
 Any other value of r0/x0 triggers a hypervisor-specific handling,
 which is not documented here.
 
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#28 lore raw

PATCH v3 18/21 arm64: Move "nokaslr" over to the early cpufeature infrastructure

In reply to Marc Zyngier

Given that the early cpufeature infrastructure has borrowed quite a lot of code from the kaslr implementation, let's reimplement the matching of the "nokaslr" option with it.

---
 arch/arm64/kernel/idreg-override.c | 17 ++++++++++++++
 arch/arm64/kernel/kaslr.c          | 37 +++---------------------------
 2 files changed, 20 insertions(+), 34 deletions(-)
arch/arm64/kernel/idreg-override.c +17 -0
index 1db54878b2c4..143fe7b8e3ce 100644
@@ -33,8 +33,24 @@ static const struct reg_desc mmfr1 __initdata = {
 	},
 };
 
+extern u64 kaslr_feature_val;
+extern u64 kaslr_feature_mask;
+
+static const struct reg_desc kaslr __initdata = {
+	.name		= "kaslr",
+#ifdef CONFIG_RANDOMIZE_BASE
+	.val		= &kaslr_feature_val,
+	.mask		= &kaslr_feature_mask,
+#endif
+	.fields		= {
+		{ "disabled", 0 },
+		{}
+	},
+};
+
 static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
+	&kaslr,
 };
 
 static const struct {
@@ -43,6 +59,7 @@ static const struct {
 } aliases[] __initdata = {
 	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
 	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
+	{ "nokaslr",			"kaslr.disabled=1" },
 };
 
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
arch/arm64/kernel/kaslr.c +3 -34
index 5fc86e7d01a1..dcc4a5aadbe2 100644
@@ -51,39 +51,8 @@ static __init u64 get_kaslr_seed(void *fdt)
 	return ret;
 }
 
-static __init bool cmdline_contains_nokaslr(const u8 *cmdline)
-{
-	const u8 *str;
-
-	str = strstr(cmdline, "nokaslr");
-	return str == cmdline || (str > cmdline && *(str - 1) == ' ');
-}
-
-static __init bool is_kaslr_disabled_cmdline(void *fdt)
-{
-	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
-		int node;
-		const u8 *prop;
-
-		node = fdt_path_offset(fdt, "/chosen");
-		if (node < 0)
-			goto out;
-
-		prop = fdt_getprop(fdt, node, "bootargs", NULL);
-		if (!prop)
-			goto out;
-
-		if (cmdline_contains_nokaslr(prop))
-			return true;
-
-		if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
-			goto out;
-
-		return false;
-	}
-out:
-	return cmdline_contains_nokaslr(CONFIG_CMDLINE);
-}
+u64 kaslr_feature_val __initdata;
+u64 kaslr_feature_mask __initdata;
 
 /*
  * This routine will be executed with the kernel mapped at its default virtual
@@ -126,7 +95,7 @@ u64 __init kaslr_early_init(void)
 	 * Check if 'nokaslr' appears on the command line, and
 	 * return 0 if that is the case.
 	 */
-	if (is_kaslr_disabled_cmdline(fdt)) {
+	if (kaslr_feature_val & kaslr_feature_mask & 0xf) {
 		kaslr_status = KASLR_DISABLED_CMDLINE;
 		return 0;
 	}
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#29 lore raw

PATCH v3 19/21 arm64: cpufeatures: Allow disabling of BTI from the command-line

In reply to Marc Zyngier

In order to be able to disable BTI at runtime, whether it is for testing purposes, or to work around HW issues, let's add support for overriding the ID_AA64PFR1_EL1.BTI field.

This is further mapped on the arm64.nobti command-line alias.

---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 arch/arm64/include/asm/cpufeature.h             |  2 ++
 arch/arm64/kernel/cpufeature.c                  |  5 ++++-
 arch/arm64/kernel/idreg-override.c              | 12 ++++++++++++
 arch/arm64/mm/mmu.c                             |  2 +-
 5 files changed, 22 insertions(+), 2 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +3 -0
index 2786fd39a047..7599fd0f1ad7 100644
@@ -373,6 +373,9 @@
 	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 			Format: <io>,<irq>,<nodeID>
 
+	arm64.nobti	[ARM64] Unconditionally disable Branch Target
+			Identification support
+
 	ataflop=	[HW,M68k]
 
 	atarimouse=	[HW,MOUSE] Atari Mouse
arch/arm64/include/asm/cpufeature.h +2 -0
index 80a5f423444e..d3e0f6dd43c4 100644
@@ -816,6 +816,8 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
 
 extern u64 id_aa64mmfr1_val;
 extern u64 id_aa64mmfr1_mask;
+extern u64 id_aa64pfr1_val;
+extern u64 id_aa64pfr1_mask;
 
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);
arch/arm64/kernel/cpufeature.c +4 -1
index cc435b3dcd53..48dc0333bb4b 100644
@@ -557,6 +557,8 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 
 u64 id_aa64mmfr1_val;
 u64 id_aa64mmfr1_mask;
+u64 id_aa64pfr1_val;
+u64 id_aa64pfr1_mask;
 
 static const struct __ftr_reg_entry {
 	u32			sys_id;
@@ -592,7 +594,8 @@ static const struct __ftr_reg_entry {
 
 	/* Op1 = 0, CRn = 0, CRm = 4 */
 	ARM64_FTR_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0),
-	ARM64_FTR_REG(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1),
+	ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1,
+			       &id_aa64pfr1_val, &id_aa64pfr1_mask),
 	ARM64_FTR_REG(SYS_ID_AA64ZFR0_EL1, ftr_id_aa64zfr0),
 
 	/* Op1 = 0, CRn = 0, CRm = 5 */
arch/arm64/kernel/idreg-override.c +12 -0
index 143fe7b8e3ce..a9e3ed193fd4 100644
@@ -33,6 +33,16 @@ static const struct reg_desc mmfr1 __initdata = {
 	},
 };
 
+static const struct reg_desc pfr1 __initdata = {
+	.name		= "id_aa64pfr1",
+	.val		= &id_aa64pfr1_val,
+	.mask		= &id_aa64pfr1_mask,
+	.fields		= {
+	        { "bt", ID_AA64PFR1_BT_SHIFT },
+		{}
+	},
+};
+
 extern u64 kaslr_feature_val;
 extern u64 kaslr_feature_mask;
 
@@ -50,6 +60,7 @@ static const struct reg_desc kaslr __initdata = {
 
 static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
+	&pfr1,
 	&kaslr,
 };
 
@@ -59,6 +70,7 @@ static const struct {
 } aliases[] __initdata = {
 	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
 	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
+	{ "arm64.nobti",		"id_aa64pfr1.bt=0" },
 	{ "nokaslr",			"kaslr.disabled=1" },
 };
 
arch/arm64/mm/mmu.c +1 -1
index ae0c3d023824..617e704c980b 100644
@@ -628,7 +628,7 @@ static bool arm64_early_this_cpu_has_bti(void)
 	if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
 		return false;
 
-	pfr1 = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
+	pfr1 = __read_sysreg_by_encoding(SYS_ID_AA64PFR1_EL1);
 	return cpuid_feature_extract_unsigned_field(pfr1,
 						    ID_AA64PFR1_BT_SHIFT);
 }
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#30 lore raw

PATCH v3 20/21 arm64: Defer enabling pointer authentication on boot core

In reply to Marc Zyngier

From: Srinivas Ramana <[email protected]>

Defer enabling pointer authentication on boot core until after its required to be enabled by cpufeature framework. This will help in controlling the feature dynamically with a boot parameter.

---
 arch/arm64/include/asm/pointer_auth.h   | 10 ++++++++++
 arch/arm64/include/asm/stackprotector.h |  1 +
 arch/arm64/kernel/head.S                |  4 ----
 3 files changed, 11 insertions(+), 4 deletions(-)
arch/arm64/include/asm/pointer_auth.h +10 -0
index c6b4f0603024..b112a11e9302 100644
@@ -76,6 +76,15 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	return ptrauth_clear_pac(ptr);
 }
 
+static __always_inline void ptrauth_enable(void)
+{
+	if (!system_supports_address_auth())
+		return;
+	sysreg_clear_set(sctlr_el1, 0, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
+					SCTLR_ELx_ENDA | SCTLR_ELx_ENDB));
+	isb();
+}
+
 #define ptrauth_thread_init_user(tsk)					\
 	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
 #define ptrauth_thread_init_kernel(tsk)					\
@@ -84,6 +93,7 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
+#define ptrauth_enable()
 #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)
 #define ptrauth_strip_insn_pac(lr)	(lr)
 #define ptrauth_thread_init_user(tsk)
arch/arm64/include/asm/stackprotector.h +1 -0
index 7263e0bac680..33f1bb453150 100644
@@ -41,6 +41,7 @@ static __always_inline void boot_init_stack_canary(void)
 #endif
 	ptrauth_thread_init_kernel(current);
 	ptrauth_thread_switch_kernel(current);
+	ptrauth_enable();
 }
 
 #endif	/* _ASM_STACKPROTECTOR_H */
arch/arm64/kernel/head.S +0 -4
index b3c4dd04f74b..2a152d96d767 100644
@@ -404,10 +404,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	adr_l	x5, init_task
 	msr	sp_el0, x5			// Save thread_info
 
-#ifdef CONFIG_ARM64_PTR_AUTH
-	__ptrauth_keys_init_cpu	x5, x6, x7, x8
-#endif
-
 	adr_l	x8, vectors			// load VBAR_EL1 with virtual
 	msr	vbar_el1, x8			// vector table address
 	isb
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#31 lore raw

PATCH v3 21/21 arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line

In reply to Marc Zyngier

In order to be able to disable Pointer Authentication at runtime, whether it is for testing purposes, or to work around HW issues, let's add support for overriding the ID_AA64ISAR1_EL1.{GPI,GPA,API,APA} fields.

This is further mapped on the arm64.nopauth command-line alias.

---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 arch/arm64/include/asm/cpufeature.h             |  2 ++
 arch/arm64/kernel/cpufeature.c                  |  5 ++++-
 arch/arm64/kernel/idreg-override.c              | 17 +++++++++++++++++
 4 files changed, 26 insertions(+), 1 deletion(-)
Documentation/admin-guide/kernel-parameters.txt +3 -0
index 7599fd0f1ad7..f9cb28a39bd0 100644
@@ -376,6 +376,9 @@
 	arm64.nobti	[ARM64] Unconditionally disable Branch Target
 			Identification support
 
+	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
+			support
+
 	ataflop=	[HW,M68k]
 
 	atarimouse=	[HW,MOUSE] Atari Mouse
arch/arm64/include/asm/cpufeature.h +2 -0
index d3e0f6dd43c4..9d8dcf380ad5 100644
@@ -818,6 +818,8 @@ extern u64 id_aa64mmfr1_val;
 extern u64 id_aa64mmfr1_mask;
 extern u64 id_aa64pfr1_val;
 extern u64 id_aa64pfr1_mask;
+extern u64 id_aa64isar1_val;
+extern u64 id_aa64isar1_mask;
 
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);
arch/arm64/kernel/cpufeature.c +4 -1
index 48dc0333bb4b..894af60b9669 100644
@@ -559,6 +559,8 @@ u64 id_aa64mmfr1_val;
 u64 id_aa64mmfr1_mask;
 u64 id_aa64pfr1_val;
 u64 id_aa64pfr1_mask;
+u64 id_aa64isar1_val;
+u64 id_aa64isar1_mask;
 
 static const struct __ftr_reg_entry {
 	u32			sys_id;
@@ -604,7 +606,8 @@ static const struct __ftr_reg_entry {
 
 	/* Op1 = 0, CRn = 0, CRm = 6 */
 	ARM64_FTR_REG(SYS_ID_AA64ISAR0_EL1, ftr_id_aa64isar0),
-	ARM64_FTR_REG(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1),
+	ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1,
+			       &id_aa64isar1_val, &id_aa64isar1_mask),
 
 	/* Op1 = 0, CRn = 0, CRm = 7 */
 	ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
arch/arm64/kernel/idreg-override.c +17 -0
index a9e3ed193fd4..7037c9b214d0 100644
@@ -43,6 +43,19 @@ static const struct reg_desc pfr1 __initdata = {
 	},
 };
 
+static const struct reg_desc isar1 __initdata = {
+	.name		= "id_aa64isar1",
+	.val		= &id_aa64isar1_val,
+	.mask		= &id_aa64isar1_mask,
+	.fields		= {
+	        { "gpi", ID_AA64ISAR1_GPI_SHIFT },
+	        { "gpa", ID_AA64ISAR1_GPA_SHIFT },
+	        { "api", ID_AA64ISAR1_API_SHIFT },
+	        { "apa", ID_AA64ISAR1_APA_SHIFT },
+		{}
+	},
+};
+
 extern u64 kaslr_feature_val;
 extern u64 kaslr_feature_mask;
 
@@ -61,6 +74,7 @@ static const struct reg_desc kaslr __initdata = {
 static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
 	&pfr1,
+	&isar1,
 	&kaslr,
 };
 
@@ -71,6 +85,9 @@ static const struct {
 	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
 	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
 	{ "arm64.nobti",		"id_aa64pfr1.bt=0" },
+	{ "arm64.nopauth",
+	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
+	  "id_aa64isar1.api=0 id_aa64isar1.apa=0"	   },
 	{ "nokaslr",			"kaslr.disabled=1" },
 };
 
Signature · 6 lines
2.29.2

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