Commit-ID: 45c39fb0cc20d24da08d5bb159f57d191098104d
Gitweb: http://git.kernel.org/tip/45c39fb0cc20d24da08d5bb159f57d191098104d
Author: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
AuthorDate: Wed, 28 Nov 2012 11:50:30 -0800
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Thu, 29 Nov 2012 13:25:39 -0800
x86, cleanups: Simplify sync_core() in the case of no CPUID
Simplify the implementation of sync_core() for the case where we may
not have the CPUID instruction available.
[ v2: stylistic cleanup of the #else clause per suggestion by Borislav
Petkov. ]
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1354132230-21854-9-git-send-email-hpa@xxxxxxxxxxxxxxx
Cc: Borislav Petkov <bp@xxxxxxxxx>
---
arch/x86/include/asm/processor.h | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9a4ee46..b0d3e73 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -673,17 +673,28 @@ static inline void sync_core(void)
int tmp;
#ifdef CONFIG_M486
- if (boot_cpu_data.x86 < 5)
- /* There is no speculative execution.
- * jmp is a barrier to prefetching. */
- asm volatile("jmp 1f\n1:\n" ::: "memory");
- else
+ /*
+ * Do a CPUID if available, otherwise do a jump. The jump
+ * can conveniently enough be the jump around CPUID.
+ */
+ asm volatile("cmpl %2,%1\n\t"
+ "jl 1f\n\t"
+ "cpuid\n"
+ "1:"
+ : "=a" (tmp)
+ : "rm" (boot_cpu_data.cpuid_level), "ri" (0), "0" (1)
+ : "ebx", "ecx", "edx", "memory");
+#else
+ /*
+ * CPUID is a barrier to speculative execution.
+ * Prefetched instructions are automatically
+ * invalidated when modified.
+ */
+ asm volatile("cpuid"
+ : "=a" (tmp)
+ : "0" (1)
+ : "ebx", "ecx", "edx", "memory");
#endif
- /* cpuid is a barrier to speculative execution.
- * Prefetched instructions are automatically
- * invalidated when modified. */
- asm volatile("cpuid" : "=a" (tmp) : "0" (1)
- : "ebx", "ecx", "edx", "memory");
}
static inline void __monitor(const void *eax, unsigned long ecx,
--
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