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authorMark Rutland <mark.rutland@arm.com>2017-03-10 17:44:18 +0000
committerWill Deacon <will.deacon@arm.com>2017-03-10 17:45:16 +0000
commit14088540ad63c648e5cdf490412033f792d16b6b (patch)
tree634b7aaf1a7376f476fba53f963113d828d94673 /arch/arm64/include
parent5c2a625937ba49bc691089370638223d310cda9a (diff)
arm64: use const cap for system_uses_ttbr0_pan()
Since commit 4b65a5db362783ab ("arm64: Introduce uaccess_{disable,enable} functionality based on TTBR0_EL1"), system_uses_ttbr0_pan() has used cpus_have_cap() to determine whether PAN is present. Since commit a4023f682739439b ("arm64: Add hypervisor safe helper for checking constant capabilities"), which was introduced around the same time, cpus_have_cap() doesn't try to use a static key, and must always perform a load, test, and consitional branch (likely a tbnz for the latter two). Elsewhere, we moved to using cpus_have_const_cap(), which can use a static key (i.e. a non-conditional branch), which is patched at runtime when the feature is detected. This patch makes system_uses_ttbr0_pan() use cpus_have_const_cap(). The static key is likely a win for hot-paths like the uacccess primitives, and this makes our usage consistent regardless. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include')
-rw-r--r--arch/arm64/include/asm/cpufeature.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 05310ad8c5ab..f31c48d0cd68 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -251,7 +251,7 @@ static inline bool system_supports_fpsimd(void)
static inline bool system_uses_ttbr0_pan(void)
{
return IS_ENABLED(CONFIG_ARM64_SW_TTBR0_PAN) &&
- !cpus_have_cap(ARM64_HAS_PAN);
+ !cpus_have_const_cap(ARM64_HAS_PAN);
}
#endif /* __ASSEMBLY__ */