Messages in this thread Patch in this message | | | From | Suzuki K Poulose <> | Subject | [PATCH 1/2] arm64: Add hypervisor safe helper for checking constant capabilities | Date | Tue, 25 Oct 2016 14:50:32 +0100 |
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The hypervisor may not have full access to the kernel data structures and hence cannot safely use cpus_have_cap() helper for checking the system capability. Add a safe helper for hypervisors to check a constant system capability, which *doesn't* fall back to checking the bitmap maintained by the kernel.
Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> --- arch/arm64/include/asm/cpufeature.h | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 758d74f..ae5e994 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -9,8 +9,6 @@ #ifndef __ASM_CPUFEATURE_H #define __ASM_CPUFEATURE_H -#include <linux/jump_label.h> - #include <asm/hwcap.h> #include <asm/sysreg.h> @@ -45,6 +43,8 @@ #ifndef __ASSEMBLY__ +#include <linux/bug.h> +#include <linux/jump_label.h> #include <linux/kernel.h> /* CPU feature register tracking */ @@ -122,6 +122,16 @@ static inline bool cpu_have_feature(unsigned int num) return elf_hwcap & (1UL << num); } +/* System capability check for constant caps */ +static inline bool cpus_have_const_cap(int num) +{ + if (__builtin_constant_p(num)) + return static_branch_unlikely(&cpu_hwcap_keys[num]); + BUILD_BUG(); + /* unreachable */ + return false; +} + static inline bool cpus_have_cap(unsigned int num) { if (num >= ARM64_NCAPS) @@ -218,7 +228,7 @@ static inline bool cpu_supports_mixed_endian_el0(void) static inline bool system_supports_32bit_el0(void) { - return cpus_have_cap(ARM64_HAS_32BIT_EL0); + return cpus_have_const_cap(ARM64_HAS_32BIT_EL0); } static inline bool system_supports_mixed_endian_el0(void) -- 2.7.4
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