openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

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>
This commit is contained in:
Kevin Winchester 2009-08-10 19:56:45 -03:00 committed by Ingo Molnar
parent 0d01f31439
commit fbd8b1819e
1 changed files with 7 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/kernel/cpu/amd.c
View File

@ -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);