Commit 96e5d28a authored by Borislav Petkov's avatar Borislav Petkov Committed by Ingo Molnar

x86/cpu: Add Erratum 88 detection on AMD

Erratum 88 affects old AMD K8s, where a SWAPGS fails to cause an input
dependency on GS. Therefore, we need to MFENCE before it.

But that MFENCE is expensive and unnecessary on the remaining x86 CPUs
out there so patch it out on the CPUs which don't require it.
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rudolf Marek <r.marek@assembler.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/aec6b2df1bfc56101d4e9e2e5d5d570bf41663c6.1460075211.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0230bb03
...@@ -783,7 +783,7 @@ ENTRY(native_load_gs_index) ...@@ -783,7 +783,7 @@ ENTRY(native_load_gs_index)
SWAPGS SWAPGS
gs_change: gs_change:
movl %edi, %gs movl %edi, %gs
2: mfence /* workaround */ 2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
SWAPGS SWAPGS
popfq popfq
ret ret
......
...@@ -295,6 +295,8 @@ ...@@ -295,6 +295,8 @@
#define X86_BUG_CLFLUSH_MONITOR X86_BUG(7) /* AAI65, CLFLUSH required before MONITOR */ #define X86_BUG_CLFLUSH_MONITOR X86_BUG(7) /* AAI65, CLFLUSH required before MONITOR */
#define X86_BUG_SYSRET_SS_ATTRS X86_BUG(8) /* SYSRET doesn't fix up SS attrs */ #define X86_BUG_SYSRET_SS_ATTRS X86_BUG(8) /* SYSRET doesn't fix up SS attrs */
#define X86_BUG_NULL_SEG X86_BUG(9) /* Nulling a selector preserves the base */ #define X86_BUG_NULL_SEG X86_BUG(9) /* Nulling a selector preserves the base */
#define X86_BUG_SWAPGS_FENCE X86_BUG(10) /* SWAPGS without input dep on GS */
#ifdef CONFIG_X86_32 #ifdef CONFIG_X86_32
/* /*
......
...@@ -632,6 +632,7 @@ static void init_amd_k8(struct cpuinfo_x86 *c) ...@@ -632,6 +632,7 @@ static void init_amd_k8(struct cpuinfo_x86 *c)
*/ */
msr_set_bit(MSR_K7_HWCR, 6); msr_set_bit(MSR_K7_HWCR, 6);
#endif #endif
set_cpu_bug(c, X86_BUG_SWAPGS_FENCE);
} }
static void init_amd_gh(struct cpuinfo_x86 *c) static void init_amd_gh(struct cpuinfo_x86 *c)
......
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