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arm64: Add hypervisor safe helper for checking constant capabilities

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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. With this, make the cpus_have_cap() only
check the bitmask and force constant cap checks to use the new API
for quicker checks.

Cc: Robert Ritcher <rritcher@cavium.com>
Cc: Tirumalesh Chalamarla <tchalamarla@cavium.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Suzuki K Poulose
2016-11-08 13:56:20 +00:00
committed by Catalin Marinas
parent c02433dd6d
commit a4023f6827
4 changed files with 15 additions and 21 deletions
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19
arch/arm64/include/asm/cpufeature.h
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@@ -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 */
@@ -122,14 +122,19 @@ 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 (num >= ARM64_NCAPS)
return false;
return static_branch_unlikely(&cpu_hwcap_keys[num]);
}
static inline bool cpus_have_cap(unsigned int num)
{
if (num >= ARM64_NCAPS)
return false;
if (__builtin_constant_p(num))
return static_branch_unlikely(&cpu_hwcap_keys[num]);
else
return test_bit(num, cpu_hwcaps);
return test_bit(num, cpu_hwcaps);
}
static inline void cpus_set_cap(unsigned int num)
@@ -218,7 +223,7 @@ 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)