lkml.org 
[lkml]   [2016]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/2] arm64: Add hypervisor safe helper for checking constant capabilities
Date
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
\
 
 \ /
  Last update: 2016-10-25 15:52    [W:0.048 / U:4.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site