Re: [PATCH 3/4] UefiCpuPkg/MpInitLib: fix register restore issue in AP wakeup

["Dong, Eric" <eric.dong@intel.com>]

Reviewed-by: Eric Dong <eric.dong@intel.com>

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org]
> Sent: Monday, September 3, 2018 11:16 AM
> To: edk2-devel@lists.01.org
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; Yao,
> Jiewen <jiewen.yao@intel.com>; Laszlo Ersek <lersek@redhat.com>; Zeng,
> Star <star.zeng@intel.com>
> Subject: [edk2] [PATCH 3/4] UefiCpuPkg/MpInitLib: fix register restore issue
> in AP wakeup
> 
> The conflict issues are introduced by Stack Guard feature enabled for PEI.
> 
> The first is CR0 which should be restored after CR3 and CR4.
> Another is TR which should not be passed from BSP to AP during init phase.
> 
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: "Ware, Ryan R" <ryan.r.ware@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/MpLib.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 377876643f..709fbc1575 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -217,9 +217,9 @@ RestoreVolatileRegisters (
>    CPUID_VERSION_INFO_EDX        VersionInfoEdx;
>    IA32_TSS_DESCRIPTOR           *Tss;
> 
> -  AsmWriteCr0 (VolatileRegisters->Cr0);
>    AsmWriteCr3 (VolatileRegisters->Cr3);
>    AsmWriteCr4 (VolatileRegisters->Cr4);
> +  AsmWriteCr0 (VolatileRegisters->Cr0);
> 
>    if (IsRestoreDr) {
>      AsmCpuid (CPUID_VERSION_INFO, NULL, NULL, NULL,
> &VersionInfoEdx.Uint32); @@ -1558,7 +1558,7 @@ MpInitLibInitialize (
>    ApLoopMode  = GetApLoopMode (&MonitorFilterSize);
> 
>    //
> -  // Save BSP's Control registers for APs
> +  // Save BSP's Control registers for APs.
>    //
>    SaveVolatileRegisters (&VolatileRegisters);
> 
> @@ -1656,6 +1656,10 @@ MpInitLibInitialize (
>    //
>    CopyMem ((VOID *)ApIdtBase, (VOID *)VolatileRegisters.Idtr.Base,
> VolatileRegisters.Idtr.Limit + 1);
>    VolatileRegisters.Idtr.Base = ApIdtBase;
> +  //
> +  // Don't pass BSP's TR to APs to avoid AP init failure.
> +  //
> +  VolatileRegisters.Tr = 0;
>    CopyMem (&CpuMpData->CpuData[0].VolatileRegisters,
> &VolatileRegisters, sizeof (VolatileRegisters));
>    //
>    // Set BSP basic information
> --
> 2.16.2.windows.1
> 
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