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UefiCpuPkg/DxeMpLib: Fix bug when getting target C-State from eax 

AP will get target C-State from eax[7:4]. We do shift in ebx firstly before set
to eax. It will lead ebx is incorrect in the next time.

The fix is to set ebx to eax firstly and does shift in eax. Thus, ebx could keep
original value.

Reported-by: Laszlo Ersek <lersek@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Jeff Fan 2016-11-25 12:58:36 +08:00
parent 9f91cb01c4
commit f56379f361
1 changed files with 1 additions and 1 deletions
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2
UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
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@ -266,8 +266,8 @@ MwaitLoop:
xor ecx, ecx ; ecx = 0
xor edx, edx ; edx = 0
monitor
shl ebx, 4
mov eax, ebx ; Mwait Cx, Target C-State per eax[7:4]
shl eax, 4
mwait
jmp MwaitLoop
HltLoop: