Commit-ID: 96e5d28ae7a5250f3deb2434f1895c9daf48b1bd Gitweb: http://git.kernel.org/tip/96e5d28ae7a5250f3deb2434f1895c9daf48b1bd Author: Borislav Petkov <bp@xxxxxxx> AuthorDate: Thu, 7 Apr 2016 17:31:49 -0700 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 13 Apr 2016 10:20:42 +0200 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: Borislav Petkov <bp@xxxxxxx> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Rudolf Marek <r.marek@xxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/aec6b2df1bfc56101d4e9e2e5d5d570bf41663c6.1460075211.git.luto@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/entry/entry_64.S | 2 +- arch/x86/include/asm/cpufeatures.h | 2 ++ arch/x86/kernel/cpu/amd.c | 1 + 3 files changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 858b555..64d2033 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -783,7 +783,7 @@ ENTRY(native_load_gs_index) SWAPGS gs_change: movl %edi, %gs -2: mfence /* workaround */ +2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE SWAPGS popfq ret diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 2a05230..7bfb6b7 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -295,6 +295,8 @@ #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_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 /* diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 6e47e3a..b7cc9ef 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -632,6 +632,7 @@ static void init_amd_k8(struct cpuinfo_x86 *c) */ msr_set_bit(MSR_K7_HWCR, 6); #endif + set_cpu_bug(c, X86_BUG_SWAPGS_FENCE); } static void init_amd_gh(struct cpuinfo_x86 *c) -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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