arm64 kexec kernel patches V6

Hi All,

This series adds the core support for kexec re-boots on arm64. I have tested with the ARM VE fast model, the ARM Base model and the ARM Foundation model with various kernel config options for both the first and second stage kernels.

To load a second stage kernel and execute a kexec re-boot on arm64 my patches to kexec-tools [2], which have not yet been merged upstream, are needed.

Patches 1-3 rework the arm64 hcall mechanism to give the arm64 soft_restart() routine the ability to switch exception levels from EL1 to EL2 for kernels that were entered in EL2.

Patch 4 moves proc-macros.S from arm64/mm to arm64/include/asm so that the dcache_line_size macro it defines can be uesd by kexec's relocate kernel routine.

Patches 5-8 add the actual kexec support.

Please consider all patches for inclusion. Any comments or suggestions on how to improve are welcome.

[1] https://git.linaro.org/people/geoff.levand/linux-kexec.git
[2] https://git.linaro.org/people/geoff.levand/kexec-tools.git

Several things are known to have problems on kexec re-boot:

spin-table
----------

PROBLEM: The spin-table enable method does not implement all the methods needed for CPU hot-plug, so the first stage kernel cannot be shutdown properly.

WORK-AROUND: Upgrade to system firmware that provides PSCI enable method support, OR build the first stage kernel with CONFIG_SMP=n, OR pass 'maxcpus=1' on the first stage kernel command line.

FIX: Upgrade system firmware to provide PSCI enable method support or add missing spin-table support to the kernel.

KVM
---

PROBLEM: KVM acquires hypervisor resources on startup, but does not free those resources on shutdown, so the first stage kernel cannot be shutdown properly.

WORK-AROUND: Build the first stage kernel with CONFIG_KVM=n.

FIX: Fix KVM to support soft_restart(). KVM needs to restore default exception vectors, etc.

UEFI
----

PROBLEM: UEFI does not manage its runtime services virtual mappings in a way that is compatible with a kexec re-boot, so the second stage kernel hangs on boot-up.

WORK-AROUND: Disable UEFI in firmware, OR use EFI uboot emulation if provided by your firmware.

FIX: Fix kernel to manage UEFI virtual mappings properly.

/memreserve/
----------

PROBLEM: The use of device tree /memreserve/ entries is not compatible with kexec re-boot. The second stage kernel will use the reserved regions and the system will become unstable.

WORK-AROUND: Pass a user specified DTB using the kexec --dtb option.

FIX: Convert device tree source files (.dts) and/or bootloaders to use device tree reserved-memory nodes to specify reserved memory or provide an in kernel mechanism to export the /memreserve/ entries to user space.

ACPI
----

PROBLEM: The kernel for ACPI based systems does not export a device tree to the standard user space location of 'proc/device-tree'. Current applications expect to access device tree information from this standard location.

WORK-AROUND: Disable ACPI in firmware, OR pass 'acpi=off' on the first stage kernel command line, OR pass a user specified DTB using the kexec --dtb option.

FIX: Fix ACPI kernel support to export device tree information suitable for a kexec re-boot, and if this information is exported to somewhere other than 'proc/device-tree' update existing kexec user applications to use this new interface.

----------------------------------------------------------------
The following changes since commit 302cd37c417d59549d073a8986fd028998409cb9:

arm64: kvm: eliminate literal pool entries (2014-11-07 15:04:54 +0000)

are available in the git repository at:

git://git.linaro.org/people/geoff.levand/linux-kexec.git kexec-v6

for you to fetch changes up to 3fc5a4ba22342ccd8e7e5a09620b00f4b81667a6:

arm64/kexec: Enable kexec in the arm64 defconfig (2014-11-13 16:52:16 -0800)

----------------------------------------------------------------
Geoff Levand (8):
arm64: Convert hcalls to use ISS field
arm64: Add new hcall HVC_CALL_FUNC
arm64: Add EL2 switch to soft_restart
arm64: Move proc-macros.S to include/asm arm64/kexec: Add core kexec support arm64/kexec: Add pr_devel output arm64/kexec: Add checks for KVM and EFI arm64/kexec: Enable kexec in the arm64 defconfig

 arch/arm64/Kconfig                           |   9 ++
 arch/arm64/configs/defconfig                 |   1 +
 arch/arm64/include/asm/kexec.h               |  47 ++++++
 arch/arm64/include/asm/proc-fns.h            |   4 +-
 arch/arm64/{mm => include/asm}/proc-macros.S |   0
 arch/arm64/include/asm/virt.h                |  33 ++++
 arch/arm64/kernel/Makefile                   |   1 +
 arch/arm64/kernel/hyp-stub.S                 |  45 ++++--
 arch/arm64/kernel/machine_kexec.c            | 232 +++++++++++++++++++++++++++
 arch/arm64/kernel/process.c                  |  10 +-
 arch/arm64/kernel/relocate_kernel.S          | 160 ++++++++++++++++++
 arch/arm64/kvm/hyp.S                         |  18 ++-
 arch/arm64/mm/cache.S                        |   3 +-
 arch/arm64/mm/proc.S                         |  50 ++++--
 include/uapi/linux/kexec.h                   |   1 +
 15 files changed, 576 insertions(+), 38 deletions(-)
 create mode 100644 arch/arm64/include/asm/kexec.h
 rename arch/arm64/{mm => include/asm}/proc-macros.S (100%)
 create mode 100644 arch/arm64/kernel/machine_kexec.c
 create mode 100644 arch/arm64/kernel/relocate_kernel.S

1.9.1


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To allow for additional hcalls to be defined and to make the arm64 hcall API more consistent across exception vector routines, change the hcall implementations to use the ISS field of the ESR_EL2 register to specify the hcall type.

The existing arm64 hcall implementations are limited in that they only allow for two distinct hcalls; with the x0 register either zero, or not zero. Also, the API of the hyp-stub exception vector routines and the KVM exception vector routines differ; hyp-stub uses a non-zero value in x0 to implement __hyp_set_vectors, whereas KVM uses it to implement kvm_call_hyp.

Define three new preprocessor macros HVC_GET_VECTORS, HVC_SET_VECTORS and HVC_CALL_HYP and to be used as hcall type specifiers and convert the existing __hyp_get_vectors(), __hyp_set_vectors() and kvm_call_hyp() routines to use these new macros when executing an HVC call. Also change the corresponding hyp-stub and KVM el1_sync exception vector routines to use these new macros.

---
 arch/arm64/include/asm/virt.h | 20 ++++++++++++++++++++
 arch/arm64/kernel/hyp-stub.S  | 34 ++++++++++++++++++++++------------
 arch/arm64/kvm/hyp.S          | 18 +++++++++++-------
 3 files changed, 53 insertions(+), 19 deletions(-)

index 7a5df52..99c319c 100644
@@ -21,6 +21,26 @@
 #define BOOT_CPU_MODE_EL1	(0xe11)
 #define BOOT_CPU_MODE_EL2	(0xe12)
 
+/*
+ * HVC_GET_VECTORS - Return the value of the vbar_el2 register.
+ */
+
+#define HVC_GET_VECTORS 1
+
+/*
+ * HVC_SET_VECTORS - Set the value of the vbar_el2 register.
+ *
+ * @x0: Physical address of the new vector table.
+ */
+
+#define HVC_SET_VECTORS 2
+
+/*
+ * HVC_CALL_HYP - Execute a hyp routine.
+ */
+
+#define HVC_CALL_HYP 3
+
 #ifndef __ASSEMBLY__
 
 /*

index a272f33..9ce8746 100644
@@ -22,6 +22,7 @@
 #include <linux/irqchip/arm-gic-v3.h>
 
 #include <asm/assembler.h>
+#include <asm/kvm_arm.h>
 #include <asm/ptrace.h>
 #include <asm/virt.h>
 

@@ -53,14 +54,22 @@ ENDPROC(__hyp_stub_vectors)
 	.align 11
 
 el1_sync:
-	mrs	x1, esr_el2
-	lsr	x1, x1, #26
-	cmp	x1, #0x16
-	b.ne	2f				// Not an HVC trap
-	cbz	x0, 1f
-	msr	vbar_el2, x0			// Set vbar_el2
+	mrs	x18, esr_el2
+	lsr	x17, x18, #ESR_EL2_EC_SHIFT
+	and	x18, x18, #ESR_EL2_ISS
+
+	cmp     x17, #ESR_EL2_EC_HVC64
+	b.ne    2f				// Not an HVC trap
+
+	cmp	x18, #HVC_GET_VECTORS
+	b.ne	1f
+	mrs	x0, vbar_el2
 	b	2f
-1:	mrs	x0, vbar_el2			// Return vbar_el2
+
+1:	cmp	x18, #HVC_SET_VECTORS
+	b.ne	2f
+	msr	vbar_el2, x0
+
 2:	eret
 ENDPROC(el1_sync)
 

@@ -100,11 +109,12 @@ ENDPROC(\label)
  * initialisation entry point.
  */
 
-ENTRY(__hyp_get_vectors)
-	mov	x0, xzr
-	// fall through
 ENTRY(__hyp_set_vectors)
-	hvc	#0
+	hvc	#HVC_SET_VECTORS
 	ret
-ENDPROC(__hyp_get_vectors)
 ENDPROC(__hyp_set_vectors)
+
+ENTRY(__hyp_get_vectors)
+	hvc	#HVC_GET_VECTORS
+	ret
+ENDPROC(__hyp_get_vectors)

index fbe909f..6d4e186 100644
@@ -26,6 +26,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/virt.h>
 
 #define CPU_GP_REG_OFFSET(x)	(CPU_GP_REGS + x)
 #define CPU_XREG_OFFSET(x)	CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)

@@ -1105,12 +1106,9 @@ __hyp_panic_str:
  * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
  * passed in r0 and r1.
  *
- * A function pointer with a value of 0 has a special meaning, and is
- * used to implement __hyp_get_vectors in the same way as in
- * arch/arm64/kernel/hyp_stub.S.
  */
 ENTRY(kvm_call_hyp)
-	hvc	#0
+	hvc	#HVC_CALL_HYP
 	ret
 ENDPROC(kvm_call_hyp)
 

@@ -1140,6 +1138,7 @@ el1_sync:					// Guest trapped into EL2
 	push	x2, x3
 
 	mrs	x1, esr_el2
+	and	x0, x1, #ESR_EL2_ISS
 	lsr	x2, x1, #ESR_EL2_EC_SHIFT
 
 	cmp	x2, #ESR_EL2_EC_HVC64

@@ -1149,15 +1148,19 @@ el1_sync:					// Guest trapped into EL2
 	cbnz	x3, el1_trap			// called HVC
 
 	/* Here, we're pretty sure the host called HVC. */
+	mov	x18, x0
 	pop	x2, x3
 	pop	x0, x1
 
-	/* Check for __hyp_get_vectors */
-	cbnz	x0, 1f
+	cmp	x18, #HVC_GET_VECTORS
+	b.ne	1f
 	mrs	x0, vbar_el2
 	b	2f
 
-1:	push	lr, xzr
+1:	cmp	x18, #HVC_CALL_HYP
+	b.ne	2f
+
+	push	lr, xzr
 
 	/*
 	 * Compute the function address in EL2, and shuffle the parameters.

@@ -1170,6 +1173,7 @@ el1_sync:					// Guest trapped into EL2
 	blr	lr
 
 	pop	lr, xzr
+
 2:	eret
 
 el1_trap:

1.9.1



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Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. During CPU reset the CPU must be brought to the exception level it had on entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism needed for this exception level switch.

---
 arch/arm64/include/asm/virt.h | 13 +++++++++++++
 arch/arm64/kernel/hyp-stub.S  | 17 ++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

index 99c319c..055e8d8 100644
@@ -41,6 +41,19 @@
 
 #define HVC_CALL_HYP 3
 
+/*
+ * HVC_CALL_FUNC - Execute a function at EL2.
+ *
+ * @x0: Physical address of the funtion to be executed.
+ * @x1: Passed as the first argument to the function.
+ * @x2: Passed as the second argument to the function.
+ * @x3: Passed as the third argument to the function.
+ *
+ * The called function must preserve the contents of register x18.
+ */
+
+#define HVC_CALL_FUNC 4
+
 #ifndef __ASSEMBLY__
 
 /*

index 9ce8746..719c726 100644
@@ -66,9 +66,20 @@ el1_sync:
 	mrs	x0, vbar_el2
 	b	2f
 
-1:	cmp	x18, #HVC_SET_VECTORS
-	b.ne	2f
-	msr	vbar_el2, x0
+1:	cmp     x18, #HVC_SET_VECTORS
+	b.ne    1f
+	msr     vbar_el2, x0
+	b       2f
+
+1:	cmp     x18, #HVC_CALL_FUNC
+	b.ne    2f
+	mov     x18, lr
+	mov     lr, x0
+	mov     x0, x1
+	mov     x1, x2
+	mov     x2, x3
+	blr     lr
+	mov     lr, x18
 
 2:	eret
 ENDPROC(el1_sync)

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When a CPU is reset it needs to be put into the exception level it had when it entered the kernel. Update cpu_reset() to accept an argument el2_switch which signals cpu_reset() to enter the soft reset address at EL2. If el2_switch is not set the soft reset address will be entered at EL1.

Update cpu_soft_restart() and soft_restart() to pass the return of is_hyp_mode_available() as the el2_switch value to cpu_reset(). Also update the comments of cpu_reset(), cpu_soft_restart() and soft_restart() to reflect this change.

---
 arch/arm64/include/asm/proc-fns.h |  4 ++--
 arch/arm64/kernel/process.c       | 10 ++++++++-
 arch/arm64/mm/proc.S              | 47 +++++++++++++++++++++++++++++----------
 3 files changed, 46 insertions(+), 15 deletions(-)

index 9a8fd84..339394d 100644
@@ -32,8 +32,8 @@ extern void cpu_cache_off(void);
 extern void cpu_do_idle(void);
 extern void cpu_do_switch_mm(unsigned long pgd_phys, struct mm_struct *mm);
 extern void cpu_reset(unsigned long addr) __attribute__((noreturn));
-void cpu_soft_restart(phys_addr_t cpu_reset,
-		unsigned long addr) __attribute__((noreturn));
+void cpu_soft_restart(phys_addr_t cpu_reset, unsigned long el2_switch,
+		      unsigned long addr) __attribute__((noreturn));
 extern void cpu_do_suspend(struct cpu_suspend_ctx *ptr);
 extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);
 

index fde9923..371bbf1 100644
@@ -50,6 +50,7 @@
 #include <asm/mmu_context.h>
 #include <asm/processor.h>
 #include <asm/stacktrace.h>
+#include <asm/virt.h>
 
 #ifdef CONFIG_CC_STACKPROTECTOR
 #include <linux/stackprotector.h>

@@ -60,7 +61,14 @@ EXPORT_SYMBOL(__stack_chk_guard);
 void soft_restart(unsigned long addr)
 {
 	setup_mm_for_reboot();
-	cpu_soft_restart(virt_to_phys(cpu_reset), addr);
+
+	/* TODO: Remove this conditional when KVM can support CPU restart. */
+	if (IS_ENABLED(CONFIG_KVM))
+		cpu_soft_restart(virt_to_phys(cpu_reset), 0, addr);
+	else
+		cpu_soft_restart(virt_to_phys(cpu_reset),
+				 is_hyp_mode_available(), addr);
+
 	/* Should never get here */
 	BUG();
 }

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To allow the assembler macros defined in proc-macros.S to be used outside the mm code move the proc-macros.S file from arch/arm64/mm/ to arch/arm64/include/asm/ and fix up any preprocessor includes to use the new file location.

---
 arch/arm64/include/asm/proc-macros.S | 54 ++++++++++++++++++++++++++++++++++++
 arch/arm64/mm/cache.S                |  3 +-
 arch/arm64/mm/proc-macros.S          | 54 ------------------------------------
 arch/arm64/mm/proc.S                 |  3 +-
 4 files changed, 56 insertions(+), 58 deletions(-)
 create mode 100644 arch/arm64/include/asm/proc-macros.S
 delete mode 100644 arch/arm64/mm/proc-macros.S

new file mode 100644
index 0000000..005d29e
@@ -0,0 +1,54 @@
+/*
+ * Based on arch/arm/mm/proc-macros.S
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <asm/asm-offsets.h>
+#include <asm/thread_info.h>
+
+/*
+ * vma_vm_mm - get mm pointer from vma pointer (vma->vm_mm)
+ */
+	.macro	vma_vm_mm, rd, rn
+	ldr	\rd, [\rn, #VMA_VM_MM]
+	.endm
+
+/*
+ * mmid - get context id from mm pointer (mm->context.id)
+ */
+	.macro	mmid, rd, rn
+	ldr	\rd, [\rn, #MM_CONTEXT_ID]
+	.endm
+
+/*
+ * dcache_line_size - get the minimum D-cache line size from the CTR register.
+ */
+	.macro	dcache_line_size, reg, tmp
+	mrs	\tmp, ctr_el0			// read CTR
+	ubfm	\tmp, \tmp, #16, #19		// cache line size encoding
+	mov	\reg, #4			// bytes per word
+	lsl	\reg, \reg, \tmp		// actual cache line size
+	.endm
+
+/*
+ * icache_line_size - get the minimum I-cache line size from the CTR register.
+ */
+	.macro	icache_line_size, reg, tmp
+	mrs	\tmp, ctr_el0			// read CTR
+	and	\tmp, \tmp, #0xf		// cache line size encoding
+	mov	\reg, #4			// bytes per word
+	lsl	\reg, \reg, \tmp		// actual cache line size
+	.endm

index 2366383..4e811a4 100644
@@ -20,8 +20,7 @@
 #include <linux/linkage.h>
 #include <linux/init.h>
 #include <asm/assembler.h>
-
-#include "proc-macros.S"
+#include <asm/proc-macros.S>
 
 /*
  *	__flush_dcache_all()

index 7467199..b767032 100644
@@ -25,10 +25,9 @@
 #include <asm/hwcap.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/pgtable.h>
+#include <asm/proc-macros.S>
 #include <asm/virt.h>
 
-#include "proc-macros.S"
-
 #ifdef CONFIG_ARM64_64K_PAGES
 #define TCR_TG_FLAGS	TCR_TG0_64K | TCR_TG1_64K
 #else

1.9.1



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Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the arm64 architecture that add support for the kexec re-boot mechanism (CONFIG_KEXEC) on arm64 platforms.

---
 arch/arm64/Kconfig                  |   9 ++
 arch/arm64/include/asm/kexec.h      |  47 +++++++++++
 arch/arm64/kernel/Makefile          |   1 +
 arch/arm64/kernel/machine_kexec.c   | 155 ++++++++++++++++++++++++++++++++++
 arch/arm64/kernel/relocate_kernel.S | 160 ++++++++++++++++++++++++++++++++++++
 include/uapi/linux/kexec.h          |   1 +
 6 files changed, 373 insertions(+)
 create mode 100644 arch/arm64/include/asm/kexec.h
 create mode 100644 arch/arm64/kernel/machine_kexec.c
 create mode 100644 arch/arm64/kernel/relocate_kernel.S

index 1e0e467..36b7c54 100644
@@ -347,6 +347,15 @@ config ARCH_HAS_CACHE_LINE_SIZE
 
 source "mm/Kconfig"
 
+config KEXEC
+	depends on (!SMP || PM_SLEEP_SMP)
+	bool "kexec system call"
+	---help---
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel.  It is like a reboot
+	  but it is independent of the system firmware.   And like a reboot
+	  you can start any kernel with it, not just Linux.
+
 config XEN_DOM0
 	def_bool y
 	depends on XEN

index 5bd029b..49de6f8 100644
@@ -31,6 +31,7 @@ arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
 arm64-obj-$(CONFIG_KGDB)		+= kgdb.o
 arm64-obj-$(CONFIG_EFI)			+= efi.o efi-stub.o efi-entry.o
 arm64-obj-$(CONFIG_PCI)			+= pci.o
+arm64-obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
 
 obj-y					+= $(arm64-obj-y) vdso/
 obj-m					+= $(arm64-obj-m)

index 6925f5b..04626b9 100644
@@ -39,6 +39,7 @@
 #define KEXEC_ARCH_SH      (42 << 16)
 #define KEXEC_ARCH_MIPS_LE (10 << 16)
 #define KEXEC_ARCH_MIPS    ( 8 << 16)
+#define KEXEC_ARCH_ARM64   (183 << 16)
 
 /* The artificial cap on the number of segments passed to kexec_load. */
 #define KEXEC_SEGMENT_MAX 16

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To aid in debugging kexec problems or when adding new functionality to kexec add a new routine kexec_image_info() and several inline pr_devel statements.

---
 arch/arm64/kernel/machine_kexec.c | 55 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

index b0e5d76..775bcc3 100644
@@ -35,6 +35,38 @@ static bool kexec_is_dtb(const void *dtb)
 }
 
 /**
+ * kexec_image_info - For debugging output.
+ */
+#define kexec_image_info(_i) _kexec_image_info(__func__, __LINE__, _i)
+static void _kexec_image_info(const char *func, int line,
+	const struct kimage *image)
+{
+	unsigned long i;
+
+#if !defined(DEBUG)
+	return;
+#endif
+	pr_devel("%s:%d:\n", func, line);
+	pr_devel("  kexec image info:\n");
+	pr_devel("    type:        %d\n", image->type);
+	pr_devel("    start:       %lx\n", image->start);
+	pr_devel("    head:        %lx\n", image->head);
+	pr_devel("    nr_segments: %lu\n", image->nr_segments);
+
+	for (i = 0; i < image->nr_segments; i++) {
+		pr_devel("      segment[%lu]: %016lx - %016lx, "
+			"%lx bytes, %lu pages%s\n",
+			i,
+			image->segment[i].mem,
+			image->segment[i].mem + image->segment[i].memsz,
+			image->segment[i].memsz,
+			image->segment[i].memsz /  PAGE_SIZE,
+			(kexec_is_dtb(image->segment[i].buf) ?
+				", dtb segment" : ""));
+	}
+}
+
+/**
  * kexec_find_dtb_seg - Helper routine to find the dtb segment.
  */
 static const struct kexec_segment *kexec_find_dtb_seg(

@@ -67,6 +99,8 @@ int machine_kexec_prepare(struct kimage *image)
 	arm64_kexec_dtb_addr = dtb_seg ? dtb_seg->mem : 0;
 	arm64_kexec_kimage_start = image->start;
 
+	kexec_image_info(image);
+
 	return 0;
 }
 

@@ -121,6 +155,27 @@ void machine_kexec(struct kimage *image)
 	reboot_code_buffer_phys = page_to_phys(image->control_code_page);
 	reboot_code_buffer = phys_to_virt(reboot_code_buffer_phys);
 
+	kexec_image_info(image);
+
+	pr_devel("%s:%d: control_code_page:        %p\n", __func__, __LINE__,
+		image->control_code_page);
+	pr_devel("%s:%d: reboot_code_buffer_phys:  %pa\n", __func__, __LINE__,
+		&reboot_code_buffer_phys);
+	pr_devel("%s:%d: reboot_code_buffer:       %p\n", __func__, __LINE__,
+		reboot_code_buffer);
+	pr_devel("%s:%d: relocate_new_kernel:      %p\n", __func__, __LINE__,
+		relocate_new_kernel);
+	pr_devel("%s:%d: relocate_new_kernel_size: 0x%lx(%lu) bytes\n",
+		__func__, __LINE__, relocate_new_kernel_size,
+		relocate_new_kernel_size);
+
+	pr_devel("%s:%d: kexec_dtb_addr:           %lx\n", __func__, __LINE__,
+		arm64_kexec_dtb_addr);
+	pr_devel("%s:%d: kexec_kimage_head:        %lx\n", __func__, __LINE__,
+		arm64_kexec_kimage_head);
+	pr_devel("%s:%d: kexec_kimage_start:       %lx\n", __func__, __LINE__,
+		arm64_kexec_kimage_start);
+
 	/*
 	 * Copy relocate_new_kernel to the reboot_code_buffer for use
 	 * after the kernel is shut down.

1.9.1



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Add runtime checks that fail the arm64 kexec syscall for situations that would result in system instability do to problems in the KVM and EFI kernel support. These checks should be removed when the KVM and EFI problems are fixed.

---
 arch/arm64/kernel/machine_kexec.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

index 775bcc3..5b62bd1f 100644
@@ -16,6 +16,12 @@
 #include <asm/cacheflush.h>
 #include <asm/system_misc.h>
 
+/* TODO: Remove this include when KVM can support a kexc reboot. */
+#include <asm/virt.h>
+
+/* TODO: Remove this include when EFI can support a kexc reboot. */
+#include <linux/efi.h>
+
 /* Global variables for the relocate_kernel routine. */
 extern const unsigned char relocate_new_kernel[];
 extern const unsigned long relocate_new_kernel_size;

@@ -101,6 +107,22 @@ int machine_kexec_prepare(struct kimage *image)
 
 	kexec_image_info(image);
 
+	/* TODO: Remove this message when KVM can support a kexc reboot. */
+	if (IS_ENABLED(CONFIG_KVM) && is_hyp_mode_available()) {
+		pr_err("%s: Your kernel is configued with KVM support "
+			"(CONFIG_KVM=y) which currently does not allow for "
+			"kexec re-boot.\n", __func__);
+		return -ENOSYS;
+	}
+
+	/* TODO: Remove this message when EFI can support a kexc reboot. */
+	if (efi_enabled(EFI_BOOT)) {
+		pr_err("%s: Your kernel is using the Extensible Firmware "
+			"Interface (EFI) which currently does not allow for "
+			"kexec re-boot.\n", __func__);
+		return -ENOSYS;
+	}
+
 	return 0;
 }
 

1.9.1



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---
 arch/arm64/configs/defconfig | 1 +
 1 file changed, 1 insertion(+)

index 4ce602c..6a8f02a 100644
@@ -40,6 +40,7 @@ CONFIG_PREEMPT=y
 CONFIG_KSM=y
 CONFIG_TRANSPARENT_HUGEPAGE=y
 CONFIG_CMA=y
+CONFIG_KEXEC=y
 CONFIG_CMDLINE="console=ttyAMA0"
 # CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set
 CONFIG_COMPAT=y

1.9.1


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Hello.

Add runtime checks that fail the arm64 kexec syscall for situations that would result in system instability do to problems in the KVM and EFI kernel support. These checks should be removed when the KVM and EFI problems are fixed.

---
v2: Typo fixes.

 arch/arm64/kernel/machine_kexec.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

index 775bcc3..faeb4f1 100644
@@ -16,6 +16,12 @@
 #include <asm/cacheflush.h>
 #include <asm/system_misc.h>
 
+/* TODO: Remove this include when KVM can support a kexec reboot. */
+#include <asm/virt.h>
+
+/* TODO: Remove this include when EFI can support a kexec reboot. */
+#include <linux/efi.h>
+
 /* Global variables for the relocate_kernel routine. */
 extern const unsigned char relocate_new_kernel[];
 extern const unsigned long relocate_new_kernel_size;

@@ -101,6 +107,22 @@ int machine_kexec_prepare(struct kimage *image)
 
 	kexec_image_info(image);
 
+	/* TODO: Remove this message when KVM can support a kexec reboot. */
+	if (IS_ENABLED(CONFIG_KVM) && is_hyp_mode_available()) {
+		pr_err("%s: Your kernel is configured with KVM support "
+			"(CONFIG_KVM=y) which currently does not allow for "
+			"kexec re-boot.\n", __func__);
+		return -ENOSYS;
+	}
+
+	/* TODO: Remove this message when EFI can support a kexec reboot. */
+	if (efi_enabled(EFI_BOOT)) {
+		pr_err("%s: Your kernel is using the Extensible Firmware "
+			"Interface (EFI) which currently does not allow for "
+			"kexec re-boot.\n", __func__);
+		return -ENOSYS;
+	}
+
 	return 0;
 }
 

1.9.1




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[...]

Add runtime checks that fail the arm64 kexec syscall for situations that would result in system instability do to problems in the KVM and EFI kernel support. These checks should be removed when the KVM and EFI problems are fixed.

---
v2: Typo fixes.
v3: Format fixes.

 arch/arm64/kernel/machine_kexec.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

index 3d84759..e7f036e 100644
@@ -16,6 +16,12 @@
 #include <asm/cacheflush.h>
 #include <asm/system_misc.h>
 
+/* TODO: Remove this include when KVM can support a kexec reboot. */
+#include <asm/virt.h>
+
+/* TODO: Remove this include when EFI can support a kexec reboot. */
+#include <linux/efi.h>
+
 /* Global variables for the relocate_kernel routine. */
 extern const unsigned char relocate_new_kernel[];
 extern const unsigned long relocate_new_kernel_size;

@@ -100,6 +106,20 @@ int machine_kexec_prepare(struct kimage *image)
 
 	kexec_image_info(image);
 
+	/* TODO: Remove this message when KVM can support a kexec reboot. */
+	if (IS_ENABLED(CONFIG_KVM) && is_hyp_mode_available()) {
+		pr_err("%s: Your kernel is configured with KVM support (CONFIG_KVM=y) which currently does not allow for kexec re-boot.\n",
+			__func__);
+		return -ENOSYS;
+	}
+
+	/* TODO: Remove this message when EFI can support a kexec reboot. */
+	if (efi_enabled(EFI_BOOT)) {
+		pr_err("%s: Your kernel is using the Extensible Firmware Interface (EFI) which currently does not allow for kexec re-boot.\n",
+			__func__);
+		return -ENOSYS;
+	}
+
 	return 0;
 }
 

1.9.1




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To aid in debugging kexec problems or when adding new functionality to kexec add a new routine kexec_image_info() and several inline pr_devel statements.

---
v2: Format fixes - thanks Sergei

 arch/arm64/kernel/machine_kexec.c | 54 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

index b0e5d76..3d84759 100644
@@ -35,6 +35,37 @@ static bool kexec_is_dtb(const void *dtb)
 }
 
 /**
+ * kexec_image_info - For debugging output.
+ */
+#define kexec_image_info(_i) _kexec_image_info(__func__, __LINE__, _i)
+static void _kexec_image_info(const char *func, int line,
+	const struct kimage *image)
+{
+	unsigned long i;
+
+#if !defined(DEBUG)
+	return;
+#endif
+	pr_devel("%s:%d:\n", func, line);
+	pr_devel("  kexec image info:\n");
+	pr_devel("    type:        %d\n", image->type);
+	pr_devel("    start:       %lx\n", image->start);
+	pr_devel("    head:        %lx\n", image->head);
+	pr_devel("    nr_segments: %lu\n", image->nr_segments);
+
+	for (i = 0; i < image->nr_segments; i++) {
+		pr_devel("      segment[%lu]: %016lx - %016lx, %lx bytes, %lu pages%s\n",
+			i,
+			image->segment[i].mem,
+			image->segment[i].mem + image->segment[i].memsz,
+			image->segment[i].memsz,
+			image->segment[i].memsz /  PAGE_SIZE,
+			(kexec_is_dtb(image->segment[i].buf) ?
+				", dtb segment" : ""));
+	}
+}
+
+/**
  * kexec_find_dtb_seg - Helper routine to find the dtb segment.
  */
 static const struct kexec_segment *kexec_find_dtb_seg(

@@ -67,6 +98,8 @@ int machine_kexec_prepare(struct kimage *image)
 	arm64_kexec_dtb_addr = dtb_seg ? dtb_seg->mem : 0;
 	arm64_kexec_kimage_start = image->start;
 
+	kexec_image_info(image);
+
 	return 0;
 }
 

@@ -121,6 +154,27 @@ void machine_kexec(struct kimage *image)
 	reboot_code_buffer_phys = page_to_phys(image->control_code_page);
 	reboot_code_buffer = phys_to_virt(reboot_code_buffer_phys);
 
+	kexec_image_info(image);
+
+	pr_devel("%s:%d: control_code_page:        %p\n", __func__, __LINE__,
+		image->control_code_page);
+	pr_devel("%s:%d: reboot_code_buffer_phys:  %pa\n", __func__, __LINE__,
+		&reboot_code_buffer_phys);
+	pr_devel("%s:%d: reboot_code_buffer:       %p\n", __func__, __LINE__,
+		reboot_code_buffer);
+	pr_devel("%s:%d: relocate_new_kernel:      %p\n", __func__, __LINE__,
+		relocate_new_kernel);
+	pr_devel("%s:%d: relocate_new_kernel_size: 0x%lx(%lu) bytes\n",
+		__func__, __LINE__, relocate_new_kernel_size,
+		relocate_new_kernel_size);
+
+	pr_devel("%s:%d: kexec_dtb_addr:           %lx\n", __func__, __LINE__,
+		arm64_kexec_dtb_addr);
+	pr_devel("%s:%d: kexec_kimage_head:        %lx\n", __func__, __LINE__,
+		arm64_kexec_kimage_head);
+	pr_devel("%s:%d: kexec_kimage_start:       %lx\n", __func__, __LINE__,
+		arm64_kexec_kimage_start);
+
 	/*
 	 * Copy relocate_new_kernel to the reboot_code_buffer for use
 	 * after the kernel is shut down.

1.9.1




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Geoff,

Is there any Linaro card for the KVM soft restart issue?

Ccing Andrew Jones since he might be interested in KVM issues.

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Tested your master branch, works for me with below setup:
UEFI boot, CONFIG_KVM=n, maxcpus=1, --lite

But --dtb still does not work if there's no /proc/device-tree, failed as below:
unrecoverable error: could not scan "/proc/device-tree/": No such file or directory.

kexec without --lite also does not work, looks like it hangs after "Bye" ..

Thanks
Dave

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Hi Dave,

https://cards.linaro.org/browse/KWG-611

I have a skeleton patch for the fix that needs to be filled out in both in the Linaro card and in the commit (arm64/kvm:
Add KVM cpu shutdown) my master branch here:

http://git.linaro.org/people/geoff.levand/linux-kexec.git

-Geoff

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Hi Dave,

I'll be away from the office this week. I'll look into this when I return.

-Geoff

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