[PATCH v2 2/3] arm64: Add hypervisor safe helper for checking constant capabilities
From: suzuki.poulose@arm.com (Suzuki K Poulose)
Date: 2016-10-31 16:04:27
Also in:
kvmarm, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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 <redacted> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <redacted> 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