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authorKevin Winchester <kjwinchester@gmail.com>2009-08-10 19:56:45 -0300
committerIngo Molnar <mingo@elte.hu>2009-08-11 13:34:54 +0200
commitfbd8b1819e80ac5a176d085fdddc3a34d1499318 (patch)
tree7b2d450a6f64808ccf5bc6f8049a877c8db86ff0
parent0d01f31439c1e4d602bf9fdc924ab66f407f5e38 (diff)
downloadconfigs-fbd8b1819e80ac5a176d085fdddc3a34d1499318.tar.gz
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@gmail.com> Acked-by: Borislav Petkov <petkovbb@googlemail.com> LKML-Reference: <4A80A5AD.2000209@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/x86/kernel/cpu/amd.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index e2485b03f1c..63fddcd082c 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);