acpi/processor: sanitize _OSC/_PDC capabilities for Xen dom0

PATCH Superseded Jason Andryuk 4 participants 4 messages Nov 1, 2023 – Nov 8, 2023

Subsystems (4)

Stable branch x86 Xen hypervisor interface Xen hypervisor x86

lore

Share & tools

lore

Jason Andryuk

author

2023-11-01 13:42 UTC #0 lore raw

PATCH v4 1/1 acpi/processor: sanitize _OSC/_PDC capabilities for Xen dom0

From: Roger Pau Monne <[email protected]>

The Processor capability bits notify ACPI of the OS capabilities, and so ACPI can adjust the return of other Processor methods taking the OS capabilities into account.

When Linux is running as a Xen dom0, the hypervisor is the entity in charge of processor power management, and hence Xen needs to make sure the capabilities reported by _OSC/_PDC match the capabilities of the driver in Xen.

Introduce a small helper to sanitize the buffer when running as Xen dom0.

When Xen supports HWP, this serves as the equivalent of commit a21211672c9a ("ACPI / processor: Request native thermal interrupt handling via _OSC") to avoid SMM crashes. Xen will set bit ACPI_PROC_CAP_COLLAB_PROC_PERF (bit 12) in the capability bits and the _OSC/_PDC call will apply it.

[ jandryuk: Mention Xen HWP's need. Support _OSC & _PDC ]

Signed-off-by Roger Pau Monné <[email protected]>

Cc [email protected]

Signed-off-by Jason Andryuk <[email protected]>

---
v4:
Use xen_santize_proc_cap_bits() name - Michal
Rephrase comment - Michal

v3:
Move xen_sanitize_pdc() call to arch_acpi_set_proc_cap_bits() to cover _OSC and _PDC.
drivers/xen/pcpu.c is CONFIG_DOM0 && CONFIG_X86

v2:
Move local variables in acpi_processor_eval_pdc() to reuse in both conditions.

---
 arch/x86/include/asm/acpi.h           | 14 ++++++++++++++
 arch/x86/include/asm/xen/hypervisor.h |  9 +++++++++
 drivers/xen/pcpu.c                    | 21 +++++++++++++++++++++
 3 files changed, 44 insertions(+)

arch/x86/include/asm/acpi.h +14 -0

index c8a7fc23f63c..f896eed4516c 100644
@@ -16,6 +16,9 @@
 #include <asm/x86_init.h>
 #include <asm/cpufeature.h>
 #include <asm/irq_vectors.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
 
 #ifdef CONFIG_ACPI_APEI
 # include <asm/pgtable_types.h>

@@ -127,6 +130,17 @@ static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
 	if (!cpu_has(c, X86_FEATURE_MWAIT) ||
 	    boot_option_idle_override == IDLE_NOMWAIT)
 		*cap &= ~(ACPI_PROC_CAP_C_C1_FFH | ACPI_PROC_CAP_C_C2C3_FFH);
+
+	if (xen_initial_domain()) {
+		/*
+		 * When Linux is running as Xen dom0, the hypervisor is the
+		 * entity in charge of the processor power management, and so
+		 * Xen needs to check the OS capabilities reported in the
+		 * processor capabilities buffer matches what the hypervisor
+		 * driver supports.
+		 */
+		xen_sanitize_proc_cap_bits(cap);
+	}
 }
 
 static inline bool acpi_has_cpu_in_madt(void)

arch/x86/include/asm/xen/hypervisor.h +9 -0

index 7048dfacc04b..a9088250770f 100644
@@ -100,4 +100,13 @@ static inline void leave_lazy(enum xen_lazy_mode mode)
 
 enum xen_lazy_mode xen_get_lazy_mode(void);
 
+#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI)
+void xen_sanitize_proc_cap_bits(uint32_t *buf);
+#else
+static inline void xen_sanitize_proc_cap_bits(uint32_t *buf)
+{
+	BUG();
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */

drivers/xen/pcpu.c +21 -0

index b3e3d1bb37f3..7000701dff8f 100644
@@ -47,6 +47,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+#endif
 
 /*
  * @cpu_id: Xen physical cpu logic number

@@ -400,4 +403,22 @@ bool __init xen_processor_present(uint32_t acpi_id)
 
 	return online;
 }
+
+void xen_sanitize_proc_cap_bits(uint32_t *cap)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.u.set_pminfo.id	= -1,
+		.u.set_pminfo.type	= XEN_PM_PDC,
+	};
+	u32 buf[3] = { ACPI_PDC_REVISION_ID, 1, *cap };
+	int ret;
+
+	set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		pr_err("sanitize of _PDC buffer bits from Xen failed: %d\n",
+		       ret);
+	*cap = buf[2];
+}
 #endif

Signature · 1 line

2.41.0

Wilczynski, Michal

Reviewed-by on v4 1/1

2023-11-02 08:29 UTC #1 lore raw

Quoted 119 lines · Jason Andryuk

From: Roger Pau Monne <[email protected]>
The Processor capability bits notify ACPI of the OS capabilities, and so ACPI can adjust the return of other Processor methods taking the OS capabilities into account.
When Linux is running as a Xen dom0, the hypervisor is the entity in charge of processor power management, and hence Xen needs to make sure the capabilities reported by _OSC/_PDC match the capabilities of the driver in Xen.
Introduce a small helper to sanitize the buffer when running as Xen dom0.
When Xen supports HWP, this serves as the equivalent of commit a21211672c9a ("ACPI / processor: Request native thermal interrupt handling via _OSC") to avoid SMM crashes. Xen will set bit ACPI_PROC_CAP_COLLAB_PROC_PERF (bit 12) in the capability bits and the _OSC/_PDC call will apply it.
[ jandryuk: Mention Xen HWP's need. Support _OSC & _PDC ]
Signed-off-by Roger Pau Monné <[email protected]>
Cc [email protected]
Signed-off-by Jason Andryuk <[email protected]>
---
v4:
Use xen_santize_proc_cap_bits() name - Michal
Rephrase comment - Michal
v3:
Move xen_sanitize_pdc() call to arch_acpi_set_proc_cap_bits() to cover _OSC and _PDC.
drivers/xen/pcpu.c is CONFIG_DOM0 && CONFIG_X86
v2:
Move local variables in acpi_processor_eval_pdc() to reuse in both conditions.
---
 arch/x86/include/asm/acpi.h           | 14 ++++++++++++++
 arch/x86/include/asm/xen/hypervisor.h |  9 +++++++++
 drivers/xen/pcpu.c                    | 21 +++++++++++++++++++++
 3 files changed, 44 insertions(+)
arch/x86/include/asm/acpi.h +14 -0
index c8a7fc23f63c..f896eed4516c 100644
@@ -16,6 +16,9 @@
 #include <asm/x86_init.h>
 #include <asm/cpufeature.h>
 #include <asm/irq_vectors.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
 
 #ifdef CONFIG_ACPI_APEI
 # include <asm/pgtable_types.h>
@@ -127,6 +130,17 @@ static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
 	if (!cpu_has(c, X86_FEATURE_MWAIT) ||
 	    boot_option_idle_override == IDLE_NOMWAIT)
 		*cap &= ~(ACPI_PROC_CAP_C_C1_FFH | ACPI_PROC_CAP_C_C2C3_FFH);
+
+	if (xen_initial_domain()) {
+		/*
+		 * When Linux is running as Xen dom0, the hypervisor is the
+		 * entity in charge of the processor power management, and so
+		 * Xen needs to check the OS capabilities reported in the
+		 * processor capabilities buffer matches what the hypervisor
+		 * driver supports.
+		 */
+		xen_sanitize_proc_cap_bits(cap);
+	}
 }
 
 static inline bool acpi_has_cpu_in_madt(void)
arch/x86/include/asm/xen/hypervisor.h +9 -0
index 7048dfacc04b..a9088250770f 100644
@@ -100,4 +100,13 @@ static inline void leave_lazy(enum xen_lazy_mode mode)
 
 enum xen_lazy_mode xen_get_lazy_mode(void);
 
+#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI)
+void xen_sanitize_proc_cap_bits(uint32_t *buf);
+#else
+static inline void xen_sanitize_proc_cap_bits(uint32_t *buf)
+{
+	BUG();
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
drivers/xen/pcpu.c +12 -0
index b3e3d1bb37f3..7000701dff8f 100644
@@ -47,6 +47,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+#endif
 
 /*
  * @cpu_id: Xen physical cpu logic number
@@ -400,4 +403,22 @@ bool __init xen_processor_present(uint32_t acpi_id)
 
 	return online;
 }
+
+void xen_sanitize_proc_cap_bits(uint32_t *cap)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.u.set_pminfo.id	= -1,
+		.u.set_pminfo.type	= XEN_PM_PDC,
+	};
+	u32 buf[3] = { ACPI_PDC_REVISION_ID, 1, *cap };

drivers/xen/pcpu.c bool __init xen_processor_present(uint32_t acpi_id) · line 424

Quoted 10 lines

drivers/xen/pcpu.c +9 -0

+	int ret;
+
+	set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		pr_err("sanitize of _PDC buffer bits from Xen failed: %d\n",
+		       ret);
+	*cap = buf[2];
+}
 #endif

Looks good to me.
For what it's worth -

Reviewed-by Michal Wilczynski <[email protected]>

Juergen Gross

maintainer Reviewed-by on v4 1/1

2023-11-02 12:39 UTC #2 lore raw

In reply to Jason Andryuk

Quoted 20 lines · Jason Andryuk

From: Roger Pau Monne <[email protected]>
The Processor capability bits notify ACPI of the OS capabilities, and so ACPI can adjust the return of other Processor methods taking the OS capabilities into account.
When Linux is running as a Xen dom0, the hypervisor is the entity in charge of processor power management, and hence Xen needs to make sure the capabilities reported by _OSC/_PDC match the capabilities of the driver in Xen.
Introduce a small helper to sanitize the buffer when running as Xen dom0.
When Xen supports HWP, this serves as the equivalent of commit a21211672c9a ("ACPI / processor: Request native thermal interrupt handling via _OSC") to avoid SMM crashes. Xen will set bit ACPI_PROC_CAP_COLLAB_PROC_PERF (bit 12) in the capability bits and the _OSC/_PDC call will apply it.

Quoted 4 lines

[ jandryuk: Mention Xen HWP's need. Support _OSC & _PDC ]
Signed-off-by Roger Pau Monné <[email protected]>
Cc [email protected]
Signed-off-by Jason Andryuk <[email protected]>

Reviewed-by Juergen Gross <[email protected]>

Juergen

Roger Pau Monné

2023-11-08 17:02 UTC #3 lore raw

In reply to Jason Andryuk

Quoted 117 lines · Jason Andryuk

From: Roger Pau Monne <[email protected]>
The Processor capability bits notify ACPI of the OS capabilities, and so ACPI can adjust the return of other Processor methods taking the OS capabilities into account.
When Linux is running as a Xen dom0, the hypervisor is the entity in charge of processor power management, and hence Xen needs to make sure the capabilities reported by _OSC/_PDC match the capabilities of the driver in Xen.
Introduce a small helper to sanitize the buffer when running as Xen dom0.
When Xen supports HWP, this serves as the equivalent of commit a21211672c9a ("ACPI / processor: Request native thermal interrupt handling via _OSC") to avoid SMM crashes. Xen will set bit ACPI_PROC_CAP_COLLAB_PROC_PERF (bit 12) in the capability bits and the _OSC/_PDC call will apply it.
[ jandryuk: Mention Xen HWP's need. Support _OSC & _PDC ]
Signed-off-by Roger Pau Monné <[email protected]>
Cc [email protected]
Signed-off-by Jason Andryuk <[email protected]>
---
v4:
Use xen_santize_proc_cap_bits() name - Michal
Rephrase comment - Michal
v3:
Move xen_sanitize_pdc() call to arch_acpi_set_proc_cap_bits() to cover _OSC and _PDC.
drivers/xen/pcpu.c is CONFIG_DOM0 && CONFIG_X86
v2:
Move local variables in acpi_processor_eval_pdc() to reuse in both conditions.
---
 arch/x86/include/asm/acpi.h           | 14 ++++++++++++++
 arch/x86/include/asm/xen/hypervisor.h |  9 +++++++++
 drivers/xen/pcpu.c                    | 21 +++++++++++++++++++++
 3 files changed, 44 insertions(+)
arch/x86/include/asm/acpi.h +14 -0
index c8a7fc23f63c..f896eed4516c 100644
@@ -16,6 +16,9 @@
 #include <asm/x86_init.h>
 #include <asm/cpufeature.h>
 #include <asm/irq_vectors.h>
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.h>
 
 #ifdef CONFIG_ACPI_APEI
 # include <asm/pgtable_types.h>
@@ -127,6 +130,17 @@ static inline void arch_acpi_set_proc_cap_bits(u32 *cap)
 	if (!cpu_has(c, X86_FEATURE_MWAIT) ||
 	    boot_option_idle_override == IDLE_NOMWAIT)
 		*cap &= ~(ACPI_PROC_CAP_C_C1_FFH | ACPI_PROC_CAP_C_C2C3_FFH);
+
+	if (xen_initial_domain()) {
+		/*
+		 * When Linux is running as Xen dom0, the hypervisor is the
+		 * entity in charge of the processor power management, and so
+		 * Xen needs to check the OS capabilities reported in the
+		 * processor capabilities buffer matches what the hypervisor
+		 * driver supports.
+		 */
+		xen_sanitize_proc_cap_bits(cap);
+	}
 }
 
 static inline bool acpi_has_cpu_in_madt(void)
arch/x86/include/asm/xen/hypervisor.h +9 -0
index 7048dfacc04b..a9088250770f 100644
@@ -100,4 +100,13 @@ static inline void leave_lazy(enum xen_lazy_mode mode)
 
 enum xen_lazy_mode xen_get_lazy_mode(void);
 
+#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI)
+void xen_sanitize_proc_cap_bits(uint32_t *buf);
+#else
+static inline void xen_sanitize_proc_cap_bits(uint32_t *buf)
+{
+	BUG();
+}
+#endif
+
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
drivers/xen/pcpu.c +10 -0
index b3e3d1bb37f3..7000701dff8f 100644
@@ -47,6 +47,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+#endif
 
 /*
  * @cpu_id: Xen physical cpu logic number
@@ -400,4 +403,22 @@ bool __init xen_processor_present(uint32_t acpi_id)
 
 	return online;
 }
+
+void xen_sanitize_proc_cap_bits(uint32_t *cap)
+{
+	struct xen_platform_op op = {
+		.cmd			= XENPF_set_processor_pminfo,
+		.u.set_pminfo.id	= -1,
+		.u.set_pminfo.type	= XEN_PM_PDC,

drivers/xen/pcpu.c bool __init xen_processor_present(uint32_t acpi_id) · line 422

Quoted 10 lines

drivers/xen/pcpu.c +10 -0

+	};
+	u32 buf[3] = { ACPI_PDC_REVISION_ID, 1, *cap };
+	int ret;
+
+	set_xen_guest_handle(op.u.set_pminfo.pdc, buf);
+	ret = HYPERVISOR_platform_op(&op);
+	if (ret)
+		pr_err("sanitize of _PDC buffer bits from Xen failed: %d\n",
+		       ret);
+	*cap = buf[2];

FWIW, we might want to only update cap if the hypercall has been successful, otherwise there's no guarantee of what's in the buffer, so I would recommend to put the updating of cap in an else branch.

Anyway, not a strong opinion, as I think in practice even if the hypercall fails it wouldn't corrupt the data in the buffer, but seems more robust.

Thanks, Roger.