[edk2-devel] [PATCH v1] UefiCpuPkg/MpInitLib: Fix possible uninitialized 'InitFlag' field
Laszlo Ersek
lersek at redhat.com
Fri Jan 17 08:41:42 UTC 2020
On 01/17/20 07:56, Hao A Wu wrote:
> REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2474
>
> Previous commit d786a17232:
> UefiCpuPkg/MpInitLib: Reduce the size when loading microcode patches
>
> Removed the below assignments for the 'InitFlag' field of CPU_MP_DATA
> structure in function MpInitLibInitialize() when APs are waken up to do
> some initialize sync:
>
> CpuMpData->InitFlag = ApInitReconfig;
> ...
> CpuMpData->InitFlag = ApInitDone;
>
> Under some cases (e.g. when variable OldCpuMpData is not NULL, which means
> function CollectProcessorCount() will not be called), this will left the
> 'InitFlag' field being uninitialized with a value of 0, which is a invalid
> value for the type of 'InitFlag' (AP_INIT_STATE).
>
> It may potentially cause the WakeUpAP() function to run some unnecessary
> codes when the APs have been successfully waken up before:
>
> if (CpuMpData->WakeUpByInitSipiSipi ||
> CpuMpData->InitFlag != ApInitDone) {
> ResetVectorRequired = TRUE;
> AllocateResetVector (CpuMpData);
> FillExchangeInfoData (CpuMpData);
> SaveLocalApicTimerSetting (CpuMpData);
> }
>
> This commit will address the above-mentioned issue.
>
> Test done:
> * OS boot on a real platform with multi processors
>
> Cc: Eric Dong <eric.dong at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> Cc: Michael D Kinney <michael.d.kinney at intel.com>
> Signed-off-by: Hao A Wu <hao.a.wu at intel.com>
> ---
> UefiCpuPkg/Library/MpInitLib/MpLib.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 6ec9b172b8..17e19395f2 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -1775,11 +1775,12 @@ MpInitLibInitialize (
> // Wakeup APs to do some AP initialize sync (Microcode & MTRR)
> //
> if (CpuMpData->CpuCount > 1) {
> + CpuMpData->InitFlag = ApInitReconfig;
> WakeUpAP (CpuMpData, TRUE, 0, ApInitializeSync, CpuMpData, TRUE);
> while (CpuMpData->FinishedCount < (CpuMpData->CpuCount - 1)) {
> CpuPause ();
> }
> -
> + CpuMpData->InitFlag = ApInitDone;
> for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
> SetApState (&CpuMpData->CpuData[Index], CpuStateIdle);
> }
>
It looks reasonable to me, but I was away while patch
"UefiCpuPkg/MpInitLib: Reduce the size when loading microcode patches"
was being reviewed, so I can't really say.
Can you explain (in the commit message) *why* commit d786a17232 removed
these InitFlag assignments? I've now read the commit message on
d786a17232, and it's not obvious to me.
Also, it would be nice to reinstate the following comment:
//
// Wait for all APs finish initialization
//
just before the "while" statement.
Thanks
Laszlo
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