Commit-ID: fbd8b1819e80ac5a176d085fdddc3a34d1499318 Gitweb: http://git.kernel.org/tip/fbd8b1819e80ac5a176d085fdddc3a34d1499318 Author: Kevin Winchester <kjwinchester@xxxxxxxxx> AuthorDate: Mon, 10 Aug 2009 19:56:45 -0300 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Tue, 11 Aug 2009 13:34:54 +0200 x86: Clear incorrectly forced X86_FEATURE_LAHF_LM flag Due to an erratum with certain AMD Athlon 64 processors, the BIOS may need to force enable the LAHF_LM capability. Unfortunately, in at least one case, the BIOS does this even for processors that do not support the functionality. Add a specific check that will clear the feature bit for processors known not to support the LAHF/SAHF instructions. Signed-off-by: Kevin Winchester <kjwinchester@xxxxxxxxx> Acked-by: Borislav Petkov <petkovbb@xxxxxxxxxxxxxx> LKML-Reference: <4A80A5AD.2000209@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- arch/x86/kernel/cpu/amd.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index e2485b0..63fddcd 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -400,6 +400,13 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) level = cpuid_eax(1); if((level >= 0x0f48 && level < 0x0f50) || level >= 0x0f58) set_cpu_cap(c, X86_FEATURE_REP_GOOD); + + /* + * Some BIOSes incorrectly force this feature, but only K8 + * revision D (model = 0x14) and later actually support it. + */ + if (c->x86_model < 0x14) + clear_cpu_cap(c, X86_FEATURE_LAHF_LM); } if (c->x86 == 0x10 || c->x86 == 0x11) set_cpu_cap(c, X86_FEATURE_REP_GOOD); -- 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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