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@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
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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