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| author | Mark Rutland <mark.rutland@arm.com> | 2017-03-10 17:44:18 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2017-03-10 17:45:16 +0000 |
| commit | 14088540ad63c648e5cdf490412033f792d16b6b (patch) | |
| tree | 634b7aaf1a7376f476fba53f963113d828d94673 /arch | |
| parent | 5c2a625937ba49bc691089370638223d310cda9a (diff) | |
| download | linux-0-day-14088540ad63c648e5cdf490412033f792d16b6b.tar.gz linux-0-day-14088540ad63c648e5cdf490412033f792d16b6b.tar.xz | |
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')
| -rw-r--r-- | arch/arm64/include/asm/cpufeature.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 05310ad8c5abe..f31c48d0cd687 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__ */ |