Hi,
6.11 already supports most functionality of AMD family 0x1a model 0x60,
but the amd-pmf driver doesn't load due to a missing device ID.
The device ID was added in 6.12 with:
commit 8ca8d07857c69 ("platform/x86/amd/pmf: Add SMU metrics table
support for 1Ah family 60h model")
Can this please come back to 6.11.y to enable it more widely?
Thanks!
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 8c462d56487e3abdbf8a61cedfe7c795a54f4a78
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110956-ungloved-yelp-6fba@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 8c462d56487e3abdbf8a61cedfe7c795a54f4a78 Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland(a)arm.com>
Date: Wed, 6 Nov 2024 16:04:48 +0000
Subject: [PATCH] arm64: smccc: Remove broken support for SMCCCv1.3 SVE discard
hint
SMCCCv1.3 added a hint bit which callers can set in an SMCCC function ID
(AKA "FID") to indicate that it is acceptable for the SMCCC
implementation to discard SVE and/or SME state over a specific SMCCC
call. The kernel support for using this hint is broken and SMCCC calls
may clobber the SVE and/or SME state of arbitrary tasks, though FPSIMD
state is unaffected.
The kernel support is intended to use the hint when there is no SVE or
SME state to save, and to do this it checks whether TIF_FOREIGN_FPSTATE
is set or TIF_SVE is clear in assembly code:
| ldr <flags>, [<current_task>, #TSK_TI_FLAGS]
| tbnz <flags>, #TIF_FOREIGN_FPSTATE, 1f // Any live FP state?
| tbnz <flags>, #TIF_SVE, 2f // Does that state include SVE?
|
| 1: orr <fid>, <fid>, ARM_SMCCC_1_3_SVE_HINT
| 2:
| << SMCCC call using FID >>
This is not safe as-is:
(1) SMCCC calls can be made in a preemptible context and preemption can
result in TIF_FOREIGN_FPSTATE being set or cleared at arbitrary
points in time. Thus checking for TIF_FOREIGN_FPSTATE provides no
guarantee.
(2) TIF_FOREIGN_FPSTATE only indicates that the live FP/SVE/SME state in
the CPU does not belong to the current task, and does not indicate
that clobbering this state is acceptable.
When the live CPU state is clobbered it is necessary to update
fpsimd_last_state.st to ensure that a subsequent context switch will
reload FP/SVE/SME state from memory rather than consuming the
clobbered state. This and the SMCCC call itself must happen in a
critical section with preemption disabled to avoid races.
(3) Live SVE/SME state can exist with TIF_SVE clear (e.g. with only
TIF_SME set), and checking TIF_SVE alone is insufficient.
Remove the broken support for the SMCCCv1.3 SVE saving hint. This is
effectively a revert of commits:
* cfa7ff959a78 ("arm64: smccc: Support SMCCC v1.3 SVE register saving hint")
* a7c3acca5380 ("arm64: smccc: Save lr before calling __arm_smccc_sve_check()")
... leaving behind the ARM_SMCCC_VERSION_1_3 and ARM_SMCCC_1_3_SVE_HINT
definitions, since these are simply definitions from the SMCCC
specification, and the latter is used in KVM via ARM_SMCCC_CALL_HINTS.
If we want to bring this back in future, we'll probably want to handle
this logic in C where we can use all the usual FPSIMD/SVE/SME helper
functions, and that'll likely require some rework of the SMCCC code
and/or its callers.
Fixes: cfa7ff959a78 ("arm64: smccc: Support SMCCC v1.3 SVE register saving hint")
Signed-off-by: Mark Rutland <mark.rutland(a)arm.com>
Cc: Ard Biesheuvel <ardb(a)kernel.org>
Cc: Catalin Marinas <catalin.marinas(a)arm.com>
Cc: Marc Zyngier <maz(a)kernel.org>
Cc: Mark Brown <broonie(a)kernel.org>
Cc: Will Deacon <will(a)kernel.org>
Cc: stable(a)vger.kernel.org
Reviewed-by: Mark Brown <broonie(a)kernel.org>
Link: https://lore.kernel.org/r/20241106160448.2712997-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will(a)kernel.org>
diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index 487381164ff6..2def9d0dd3dd 100644
--- a/arch/arm64/kernel/smccc-call.S
+++ b/arch/arm64/kernel/smccc-call.S
@@ -7,48 +7,19 @@
#include <asm/asm-offsets.h>
#include <asm/assembler.h>
-#include <asm/thread_info.h>
-
-/*
- * If we have SMCCC v1.3 and (as is likely) no SVE state in
- * the registers then set the SMCCC hint bit to say there's no
- * need to preserve it. Do this by directly adjusting the SMCCC
- * function value which is already stored in x0 ready to be called.
- */
-SYM_FUNC_START(__arm_smccc_sve_check)
-
- ldr_l x16, smccc_has_sve_hint
- cbz x16, 2f
-
- get_current_task x16
- ldr x16, [x16, #TSK_TI_FLAGS]
- tbnz x16, #TIF_FOREIGN_FPSTATE, 1f // Any live FP state?
- tbnz x16, #TIF_SVE, 2f // Does that state include SVE?
-
-1: orr x0, x0, ARM_SMCCC_1_3_SVE_HINT
-
-2: ret
-SYM_FUNC_END(__arm_smccc_sve_check)
-EXPORT_SYMBOL(__arm_smccc_sve_check)
.macro SMCCC instr
- stp x29, x30, [sp, #-16]!
- mov x29, sp
-alternative_if ARM64_SVE
- bl __arm_smccc_sve_check
-alternative_else_nop_endif
\instr #0
- ldr x4, [sp, #16]
+ ldr x4, [sp]
stp x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
stp x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
- ldr x4, [sp, #24]
+ ldr x4, [sp, #8]
cbz x4, 1f /* no quirk structure */
ldr x9, [x4, #ARM_SMCCC_QUIRK_ID_OFFS]
cmp x9, #ARM_SMCCC_QUIRK_QCOM_A6
b.ne 1f
str x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS]
-1: ldp x29, x30, [sp], #16
- ret
+1: ret
.endm
/*
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index d670635914ec..a74600d9f2d7 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -16,7 +16,6 @@ static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
bool __ro_after_init smccc_trng_available = false;
-u64 __ro_after_init smccc_has_sve_hint = false;
s32 __ro_after_init smccc_soc_id_version = SMCCC_RET_NOT_SUPPORTED;
s32 __ro_after_init smccc_soc_id_revision = SMCCC_RET_NOT_SUPPORTED;
@@ -28,9 +27,6 @@ void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
smccc_conduit = conduit;
smccc_trng_available = smccc_probe_trng();
- if (IS_ENABLED(CONFIG_ARM64_SVE) &&
- smccc_version >= ARM_SMCCC_VERSION_1_3)
- smccc_has_sve_hint = true;
if ((smccc_version >= ARM_SMCCC_VERSION_1_2) &&
(smccc_conduit != SMCCC_CONDUIT_NONE)) {
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index f59099a213d0..67f6fdf2e7cd 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -315,8 +315,6 @@ u32 arm_smccc_get_version(void);
void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit);
-extern u64 smccc_has_sve_hint;
-
/**
* arm_smccc_get_soc_id_version()
*
@@ -414,15 +412,6 @@ struct arm_smccc_quirk {
} state;
};
-/**
- * __arm_smccc_sve_check() - Set the SVE hint bit when doing SMC calls
- *
- * Sets the SMCCC hint bit to indicate if there is live state in the SVE
- * registers, this modifies x0 in place and should never be called from C
- * code.
- */
-asmlinkage unsigned long __arm_smccc_sve_check(unsigned long x0);
-
/**
* __arm_smccc_smc() - make SMC calls
* @a0-a7: arguments passed in registers 0 to 7
@@ -490,20 +479,6 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
#endif
-/* nVHE hypervisor doesn't have a current thread so needs separate checks */
-#if defined(CONFIG_ARM64_SVE) && !defined(__KVM_NVHE_HYPERVISOR__)
-
-#define SMCCC_SVE_CHECK ALTERNATIVE("nop \n", "bl __arm_smccc_sve_check \n", \
- ARM64_SVE)
-#define smccc_sve_clobbers "x16", "x30", "cc",
-
-#else
-
-#define SMCCC_SVE_CHECK
-#define smccc_sve_clobbers
-
-#endif
-
#define __constraint_read_2 "r" (arg0)
#define __constraint_read_3 __constraint_read_2, "r" (arg1)
#define __constraint_read_4 __constraint_read_3, "r" (arg2)
@@ -574,12 +549,11 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
register unsigned long r3 asm("r3"); \
CONCATENATE(__declare_arg_, \
COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__); \
- asm volatile(SMCCC_SVE_CHECK \
- inst "\n" : \
+ asm volatile(inst "\n" : \
"=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3) \
: CONCATENATE(__constraint_read_, \
COUNT_ARGS(__VA_ARGS__)) \
- : smccc_sve_clobbers "memory"); \
+ : "memory"); \
if (___res) \
*___res = (typeof(*___res)){r0, r1, r2, r3}; \
} while (0)
@@ -628,7 +602,7 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
asm ("" : \
: CONCATENATE(__constraint_read_, \
COUNT_ARGS(__VA_ARGS__)) \
- : smccc_sve_clobbers "memory"); \
+ : "memory"); \
if (___res) \
___res->a0 = SMCCC_RET_NOT_SUPPORTED; \
} while (0)
The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 8c462d56487e3abdbf8a61cedfe7c795a54f4a78
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110954-gambling-matador-1fff@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 8c462d56487e3abdbf8a61cedfe7c795a54f4a78 Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland(a)arm.com>
Date: Wed, 6 Nov 2024 16:04:48 +0000
Subject: [PATCH] arm64: smccc: Remove broken support for SMCCCv1.3 SVE discard
hint
SMCCCv1.3 added a hint bit which callers can set in an SMCCC function ID
(AKA "FID") to indicate that it is acceptable for the SMCCC
implementation to discard SVE and/or SME state over a specific SMCCC
call. The kernel support for using this hint is broken and SMCCC calls
may clobber the SVE and/or SME state of arbitrary tasks, though FPSIMD
state is unaffected.
The kernel support is intended to use the hint when there is no SVE or
SME state to save, and to do this it checks whether TIF_FOREIGN_FPSTATE
is set or TIF_SVE is clear in assembly code:
| ldr <flags>, [<current_task>, #TSK_TI_FLAGS]
| tbnz <flags>, #TIF_FOREIGN_FPSTATE, 1f // Any live FP state?
| tbnz <flags>, #TIF_SVE, 2f // Does that state include SVE?
|
| 1: orr <fid>, <fid>, ARM_SMCCC_1_3_SVE_HINT
| 2:
| << SMCCC call using FID >>
This is not safe as-is:
(1) SMCCC calls can be made in a preemptible context and preemption can
result in TIF_FOREIGN_FPSTATE being set or cleared at arbitrary
points in time. Thus checking for TIF_FOREIGN_FPSTATE provides no
guarantee.
(2) TIF_FOREIGN_FPSTATE only indicates that the live FP/SVE/SME state in
the CPU does not belong to the current task, and does not indicate
that clobbering this state is acceptable.
When the live CPU state is clobbered it is necessary to update
fpsimd_last_state.st to ensure that a subsequent context switch will
reload FP/SVE/SME state from memory rather than consuming the
clobbered state. This and the SMCCC call itself must happen in a
critical section with preemption disabled to avoid races.
(3) Live SVE/SME state can exist with TIF_SVE clear (e.g. with only
TIF_SME set), and checking TIF_SVE alone is insufficient.
Remove the broken support for the SMCCCv1.3 SVE saving hint. This is
effectively a revert of commits:
* cfa7ff959a78 ("arm64: smccc: Support SMCCC v1.3 SVE register saving hint")
* a7c3acca5380 ("arm64: smccc: Save lr before calling __arm_smccc_sve_check()")
... leaving behind the ARM_SMCCC_VERSION_1_3 and ARM_SMCCC_1_3_SVE_HINT
definitions, since these are simply definitions from the SMCCC
specification, and the latter is used in KVM via ARM_SMCCC_CALL_HINTS.
If we want to bring this back in future, we'll probably want to handle
this logic in C where we can use all the usual FPSIMD/SVE/SME helper
functions, and that'll likely require some rework of the SMCCC code
and/or its callers.
Fixes: cfa7ff959a78 ("arm64: smccc: Support SMCCC v1.3 SVE register saving hint")
Signed-off-by: Mark Rutland <mark.rutland(a)arm.com>
Cc: Ard Biesheuvel <ardb(a)kernel.org>
Cc: Catalin Marinas <catalin.marinas(a)arm.com>
Cc: Marc Zyngier <maz(a)kernel.org>
Cc: Mark Brown <broonie(a)kernel.org>
Cc: Will Deacon <will(a)kernel.org>
Cc: stable(a)vger.kernel.org
Reviewed-by: Mark Brown <broonie(a)kernel.org>
Link: https://lore.kernel.org/r/20241106160448.2712997-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will(a)kernel.org>
diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index 487381164ff6..2def9d0dd3dd 100644
--- a/arch/arm64/kernel/smccc-call.S
+++ b/arch/arm64/kernel/smccc-call.S
@@ -7,48 +7,19 @@
#include <asm/asm-offsets.h>
#include <asm/assembler.h>
-#include <asm/thread_info.h>
-
-/*
- * If we have SMCCC v1.3 and (as is likely) no SVE state in
- * the registers then set the SMCCC hint bit to say there's no
- * need to preserve it. Do this by directly adjusting the SMCCC
- * function value which is already stored in x0 ready to be called.
- */
-SYM_FUNC_START(__arm_smccc_sve_check)
-
- ldr_l x16, smccc_has_sve_hint
- cbz x16, 2f
-
- get_current_task x16
- ldr x16, [x16, #TSK_TI_FLAGS]
- tbnz x16, #TIF_FOREIGN_FPSTATE, 1f // Any live FP state?
- tbnz x16, #TIF_SVE, 2f // Does that state include SVE?
-
-1: orr x0, x0, ARM_SMCCC_1_3_SVE_HINT
-
-2: ret
-SYM_FUNC_END(__arm_smccc_sve_check)
-EXPORT_SYMBOL(__arm_smccc_sve_check)
.macro SMCCC instr
- stp x29, x30, [sp, #-16]!
- mov x29, sp
-alternative_if ARM64_SVE
- bl __arm_smccc_sve_check
-alternative_else_nop_endif
\instr #0
- ldr x4, [sp, #16]
+ ldr x4, [sp]
stp x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
stp x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
- ldr x4, [sp, #24]
+ ldr x4, [sp, #8]
cbz x4, 1f /* no quirk structure */
ldr x9, [x4, #ARM_SMCCC_QUIRK_ID_OFFS]
cmp x9, #ARM_SMCCC_QUIRK_QCOM_A6
b.ne 1f
str x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS]
-1: ldp x29, x30, [sp], #16
- ret
+1: ret
.endm
/*
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index d670635914ec..a74600d9f2d7 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -16,7 +16,6 @@ static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
bool __ro_after_init smccc_trng_available = false;
-u64 __ro_after_init smccc_has_sve_hint = false;
s32 __ro_after_init smccc_soc_id_version = SMCCC_RET_NOT_SUPPORTED;
s32 __ro_after_init smccc_soc_id_revision = SMCCC_RET_NOT_SUPPORTED;
@@ -28,9 +27,6 @@ void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
smccc_conduit = conduit;
smccc_trng_available = smccc_probe_trng();
- if (IS_ENABLED(CONFIG_ARM64_SVE) &&
- smccc_version >= ARM_SMCCC_VERSION_1_3)
- smccc_has_sve_hint = true;
if ((smccc_version >= ARM_SMCCC_VERSION_1_2) &&
(smccc_conduit != SMCCC_CONDUIT_NONE)) {
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index f59099a213d0..67f6fdf2e7cd 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -315,8 +315,6 @@ u32 arm_smccc_get_version(void);
void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit);
-extern u64 smccc_has_sve_hint;
-
/**
* arm_smccc_get_soc_id_version()
*
@@ -414,15 +412,6 @@ struct arm_smccc_quirk {
} state;
};
-/**
- * __arm_smccc_sve_check() - Set the SVE hint bit when doing SMC calls
- *
- * Sets the SMCCC hint bit to indicate if there is live state in the SVE
- * registers, this modifies x0 in place and should never be called from C
- * code.
- */
-asmlinkage unsigned long __arm_smccc_sve_check(unsigned long x0);
-
/**
* __arm_smccc_smc() - make SMC calls
* @a0-a7: arguments passed in registers 0 to 7
@@ -490,20 +479,6 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
#endif
-/* nVHE hypervisor doesn't have a current thread so needs separate checks */
-#if defined(CONFIG_ARM64_SVE) && !defined(__KVM_NVHE_HYPERVISOR__)
-
-#define SMCCC_SVE_CHECK ALTERNATIVE("nop \n", "bl __arm_smccc_sve_check \n", \
- ARM64_SVE)
-#define smccc_sve_clobbers "x16", "x30", "cc",
-
-#else
-
-#define SMCCC_SVE_CHECK
-#define smccc_sve_clobbers
-
-#endif
-
#define __constraint_read_2 "r" (arg0)
#define __constraint_read_3 __constraint_read_2, "r" (arg1)
#define __constraint_read_4 __constraint_read_3, "r" (arg2)
@@ -574,12 +549,11 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
register unsigned long r3 asm("r3"); \
CONCATENATE(__declare_arg_, \
COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__); \
- asm volatile(SMCCC_SVE_CHECK \
- inst "\n" : \
+ asm volatile(inst "\n" : \
"=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3) \
: CONCATENATE(__constraint_read_, \
COUNT_ARGS(__VA_ARGS__)) \
- : smccc_sve_clobbers "memory"); \
+ : "memory"); \
if (___res) \
*___res = (typeof(*___res)){r0, r1, r2, r3}; \
} while (0)
@@ -628,7 +602,7 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
asm ("" : \
: CONCATENATE(__constraint_read_, \
COUNT_ARGS(__VA_ARGS__)) \
- : smccc_sve_clobbers "memory"); \
+ : "memory"); \
if (___res) \
___res->a0 = SMCCC_RET_NOT_SUPPORTED; \
} while (0)
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 751ecf6afd6568adc98f2a6052315552c0483d18
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110930-pelt-think-f459@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 751ecf6afd6568adc98f2a6052315552c0483d18 Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie(a)kernel.org>
Date: Wed, 30 Oct 2024 20:23:50 +0000
Subject: [PATCH] arm64/sve: Discard stale CPU state when handling SVE traps
The logic for handling SVE traps manipulates saved FPSIMD/SVE state
incorrectly, and a race with preemption can result in a task having
TIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state
is stale (e.g. with SVE traps enabled). This has been observed to result
in warnings from do_sve_acc() where SVE traps are not expected while
TIF_SVE is set:
| if (test_and_set_thread_flag(TIF_SVE))
| WARN_ON(1); /* SVE access shouldn't have trapped */
Warnings of this form have been reported intermittently, e.g.
https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgq…https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@googl…
The race can occur when the SVE trap handler is preempted before and
after manipulating the saved FPSIMD/SVE state, starting and ending on
the same CPU, e.g.
| void do_sve_acc(unsigned long esr, struct pt_regs *regs)
| {
| // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled
| // task->fpsimd_cpu is 0.
| // per_cpu_ptr(&fpsimd_last_state, 0) is task.
|
| ...
|
| // Preempted; migrated from CPU 0 to CPU 1.
| // TIF_FOREIGN_FPSTATE is set.
|
| get_cpu_fpsimd_context();
|
| if (test_and_set_thread_flag(TIF_SVE))
| WARN_ON(1); /* SVE access shouldn't have trapped */
|
| sve_init_regs() {
| if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
| ...
| } else {
| fpsimd_to_sve(current);
| current->thread.fp_type = FP_STATE_SVE;
| }
| }
|
| put_cpu_fpsimd_context();
|
| // Preempted; migrated from CPU 1 to CPU 0.
| // task->fpsimd_cpu is still 0
| // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then:
| // - Stale HW state is reused (with SVE traps enabled)
| // - TIF_FOREIGN_FPSTATE is cleared
| // - A return to userspace skips HW state restore
| }
Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set
by calling fpsimd_flush_task_state() to detach from the saved CPU
state. This ensures that a subsequent context switch will not reuse the
stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the
new state to be reloaded from memory prior to a return to userspace.
Fixes: cccb78ce89c4 ("arm64/sve: Rework SVE access trap to convert state in registers")
Reported-by: Mark Rutland <mark.rutland(a)arm.com>
Signed-off-by: Mark Brown <broonie(a)kernel.org>
Cc: stable(a)vger.kernel.org
Reviewed-by: Mark Rutland <mark.rutland(a)arm.com>
Link: https://lore.kernel.org/r/20241030-arm64-fpsimd-foreign-flush-v1-1-bd7bd669…
Signed-off-by: Will Deacon <will(a)kernel.org>
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 77006df20a75..6d21971ae559 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1367,6 +1367,7 @@ static void sve_init_regs(void)
} else {
fpsimd_to_sve(current);
current->thread.fp_type = FP_STATE_SVE;
+ fpsimd_flush_task_state(current);
}
}
The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 751ecf6afd6568adc98f2a6052315552c0483d18
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110929-splendid-engine-1d44@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 751ecf6afd6568adc98f2a6052315552c0483d18 Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie(a)kernel.org>
Date: Wed, 30 Oct 2024 20:23:50 +0000
Subject: [PATCH] arm64/sve: Discard stale CPU state when handling SVE traps
The logic for handling SVE traps manipulates saved FPSIMD/SVE state
incorrectly, and a race with preemption can result in a task having
TIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state
is stale (e.g. with SVE traps enabled). This has been observed to result
in warnings from do_sve_acc() where SVE traps are not expected while
TIF_SVE is set:
| if (test_and_set_thread_flag(TIF_SVE))
| WARN_ON(1); /* SVE access shouldn't have trapped */
Warnings of this form have been reported intermittently, e.g.
https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgq…https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@googl…
The race can occur when the SVE trap handler is preempted before and
after manipulating the saved FPSIMD/SVE state, starting and ending on
the same CPU, e.g.
| void do_sve_acc(unsigned long esr, struct pt_regs *regs)
| {
| // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled
| // task->fpsimd_cpu is 0.
| // per_cpu_ptr(&fpsimd_last_state, 0) is task.
|
| ...
|
| // Preempted; migrated from CPU 0 to CPU 1.
| // TIF_FOREIGN_FPSTATE is set.
|
| get_cpu_fpsimd_context();
|
| if (test_and_set_thread_flag(TIF_SVE))
| WARN_ON(1); /* SVE access shouldn't have trapped */
|
| sve_init_regs() {
| if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
| ...
| } else {
| fpsimd_to_sve(current);
| current->thread.fp_type = FP_STATE_SVE;
| }
| }
|
| put_cpu_fpsimd_context();
|
| // Preempted; migrated from CPU 1 to CPU 0.
| // task->fpsimd_cpu is still 0
| // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then:
| // - Stale HW state is reused (with SVE traps enabled)
| // - TIF_FOREIGN_FPSTATE is cleared
| // - A return to userspace skips HW state restore
| }
Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set
by calling fpsimd_flush_task_state() to detach from the saved CPU
state. This ensures that a subsequent context switch will not reuse the
stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the
new state to be reloaded from memory prior to a return to userspace.
Fixes: cccb78ce89c4 ("arm64/sve: Rework SVE access trap to convert state in registers")
Reported-by: Mark Rutland <mark.rutland(a)arm.com>
Signed-off-by: Mark Brown <broonie(a)kernel.org>
Cc: stable(a)vger.kernel.org
Reviewed-by: Mark Rutland <mark.rutland(a)arm.com>
Link: https://lore.kernel.org/r/20241030-arm64-fpsimd-foreign-flush-v1-1-bd7bd669…
Signed-off-by: Will Deacon <will(a)kernel.org>
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 77006df20a75..6d21971ae559 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1367,6 +1367,7 @@ static void sve_init_regs(void)
} else {
fpsimd_to_sve(current);
current->thread.fp_type = FP_STATE_SVE;
+ fpsimd_flush_task_state(current);
}
}