From: Borislav Petkov Date: Mon, 31 Aug 2009 07:50:11 +0000 (+0200) Subject: x86, AMD: Disable wrongly set X86_FEATURE_LAHF_LM CPUID bit X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=6b0f43ddfa358;p=linux-beck.git 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 LKML-Reference: <1251705011-18636-3-git-send-email-petkovbb@gmail.com> Signed-off-by: H. Peter Anvin --- diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 63fddcd082cd..0a717fc6aeb6 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);