Branch: refs/heads/master
Home: https://github.com/tianocore/edk2
Commit: 4da1ebf3b3c22ec3e09cef3fe5d1da6f40895e6d
https://github.com/tianocore/edk2/commit/4da1ebf3b3c22ec3e09cef3fe5d1da6f40895e6d
Author: Jeff Fan <jeff....@intel.com>
Date: 2016-04-11 (Mon, 11 Apr 2016)
Changed paths:
M UefiCpuPkg/CpuMpPei/CpuMpPei.c
Log Message:
-----------
UefiCpuPkg/CpuMpPei: Fix potential AP mwait wakeup issue
If ApLoopMode is set to ApInMwaitLoop, AP will be placed into C-State by mwait
instruction. BSP will wakeup AP by write start-up signal in monitor address.
However, AP maybe waken by SMI/NMI/MCE and other condition. On this case, AP
will check if BSP wants to wakeup itself really. If not, AP will continue to
execute mwait to C-State.
One potential issue: BSP may not recognize AP was wakeup from C-State by other
event and BSP still writes start-up signal to wakeup AP. But AP does not aware
it and still execute mwait instruction to C-State. So, AP cannot be wakeup on
this case.
This fix is let AP to clear start-up signal when it really is wakeup to execute
AP function. And BSP will write start-up signal till AP clears it.
Cc: Michael Kinney <michael.d.kin...@intel.com>
Cc: Feng Tian <feng.t...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff....@intel.com>
Reviewed-by: Feng Tian <feng.t...@intel.com>
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