diff options
| author | Kevin Winchester <kjwinchester@gmail.com> | 2009-08-10 19:56:45 -0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-08-11 13:34:54 +0200 |
| commit | fbd8b1819e80ac5a176d085fdddc3a34d1499318 (patch) | |
| tree | 7b2d450a6f64808ccf5bc6f8049a877c8db86ff0 /arch/x86 | |
| parent | 0d01f31439c1e4d602bf9fdc924ab66f407f5e38 (diff) | |
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>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | 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 e2485b03f1cf..63fddcd082cd 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); |