Re: [PATCH v2] UefiCpuPkg\CpuSmm: Save & restore CR2 on-demand paging in SMM

["Yao, Jiewen" <jiewen.yao@intel.com>]

Reviewed-by: Jiewen.yao@intel.com

> -----Original Message-----
> From: Vanguput, Narendra K
> Sent: Thursday, March 7, 2019 3:15 AM
> To: edk2-devel@lists.01.org
> Cc: Vanguput, Narendra K <narendra.k.vanguput@intel.com>; Dong, Eric
> <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Laszlo Ersek
> <lersek@redhat.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: [PATCH v2] UefiCpuPkg\CpuSmm: Save & restore CR2 on-demand
> paging in SMM
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1593
> 
> For every SMI occurrence, save and restore CR2 register only when SMM
> on-demand paging support is enabled in 64 bit operation mode.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Vanguput Narendra K <narendra.k.vanguput@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Yao Jiewen <jiewen.yao@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index 3b0b3b52ac..5be4a2b020 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1111,10 +1111,12 @@ SmiRendezvous (
> 
>    ASSERT(CpuIndex < mMaxNumberOfCpus);
> 
> -  //
> -  // Save Cr2 because Page Fault exception in SMM may override its value
> -  //
> -  Cr2 = AsmReadCr2 ();
> +  if ((sizeof (UINTN) == sizeof (UINT64)) && (!PcdGetBool
> (PcdCpuSmmStaticPageTable))) {
> +    //
> +    // Save Cr2 because Page Fault exception in SMM may override its
> value
> +    //
> +    Cr2 = AsmReadCr2 ();
> +  }
> 
>    //
>    // Perform CPU specific entry hooks
> @@ -1253,10 +1255,12 @@ SmiRendezvous (
> 
>  Exit:
>    SmmCpuFeaturesRendezvousExit (CpuIndex);
> -  //
> -  // Restore Cr2
> -  //
> -  AsmWriteCr2 (Cr2);
> +  if ((sizeof (UINTN) == sizeof (UINT64)) && (!PcdGetBool
> (PcdCpuSmmStaticPageTable))) {
> +    //
> +    // Restore Cr2
> +    //
> +    AsmWriteCr2 (Cr2);
> +  }
>  }
> 
>  /**
> --
> 2.16.2.windows.1