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arm64/sve: Report SVE to userspace via CPUID only if supported

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Currently, the SVE field in ID_AA64PFR0_EL1 is visible
unconditionally to userspace via the CPU ID register emulation,
irrespective of the kernel config.  This means that if a kernel
configured with CONFIG_ARM64_SVE=n is run on SVE-capable hardware,
userspace will see SVE reported as present in the ID regs even
though the kernel forbids execution of SVE instructions.

This patch makes the exposure of the SVE field in ID_AA64PFR0_EL1
conditional on CONFIG_ARM64_SVE=y.

Since future architecture features are likely to encounter a
similar requirement, this patch adds a suitable helper macros for
use when declaring config-conditional ID register fields.

Fixes: 43994d824e ("arm64/sve: Detect SVE and activate runtime support")
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Dave Martin 2017-12-14 14:03:44 +00:00 committed by Will Deacon
parent 1d08a044cf
commit 3fab39997a
2 changed files with 5 additions and 1 deletions
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3
arch/arm64/include/asm/cpufeature.h
View File

@ -60,6 +60,9 @@ enum ftr_type {
#define FTR_VISIBLE true /* Feature visible to the user space */
#define FTR_HIDDEN false /* Feature is hidden from the user */
#define FTR_VISIBLE_IF_IS_ENABLED(config) \
(IS_ENABLED(config) ? FTR_VISIBLE : FTR_HIDDEN)
struct arm64_ftr_bits {
bool sign; /* Value is signed ? */
bool visible;

3
arch/arm64/kernel/cpufeature.c
View File

@ -145,7 +145,8 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4, ID_AA64PFR0_FP_NI),