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authorBorislav Petkov <borislav.petkov@amd.com>2009-08-31 09:50:11 +0200
committerH. Peter Anvin <hpa@zytor.com>2009-08-31 15:14:29 -0700
commit6b0f43ddfa358dc71ad2a2d57bce5906c1c5dc1a (patch)
tree6c25cbfcd551a794678429979ac082f0c1f4251c /arch/x86/kernel/cpu/amd.c
parent177fed1ee8d727c39601ce9fc2299b4cb25a718e (diff)
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x86, AMD: Disable wrongly set X86_FEATURE_LAHF_LM CPUID bit
fbd8b1819e80ac5a176d085fdddc3a34d1499318 turns off the bit for /proc/cpuinfo. However, a proper/full fix would be to additionally turn off the bit in the CPUID output so that future callers get correct CPU features info. Do that by basically reversing what the BIOS wrongfully does at boot. Signed-off-by: Borislav Petkov <borislav.petkov@amd.com> LKML-Reference: <1251705011-18636-3-git-send-email-petkovbb@gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/kernel/cpu/amd.c')
-rw-r--r--arch/x86/kernel/cpu/amd.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 63fddcd..0a717fc 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -404,9 +404,18 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
/*
* Some BIOSes incorrectly force this feature, but only K8
* revision D (model = 0x14) and later actually support it.
+ * (AMD Erratum #110, docId: 25759).
*/
- if (c->x86_model < 0x14)
+ if (c->x86_model < 0x14 && cpu_has(c, X86_FEATURE_LAHF_LM)) {
+ u64 val;
+
clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
+ if (!rdmsrl_amd_safe(0xc001100d, &val)) {
+ val &= ~(1ULL << 32);
+ wrmsrl_amd_safe(0xc001100d, val);
+ }
+ }
+
}
if (c->x86 == 0x10 || c->x86 == 0x11)
set_cpu_cap(c, X86_FEATURE_REP_GOOD);