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-rw-r--r--arch/x86/include/asm/processor.h16
1 files changed, 13 insertions, 3 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index ac7e79654f3..e08ea043e08 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -713,13 +713,23 @@ static inline void cpu_relax(void)
rep_nop();
}
-/* Stop speculative execution: */
+/* Stop speculative execution and prefetching of modified code. */
static inline void sync_core(void)
{
int tmp;
- asm volatile("cpuid" : "=a" (tmp) : "0" (1)
- : "ebx", "ecx", "edx", "memory");
+#if defined(CONFIG_M386) || defined(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
+#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,