Re: [PATCH 2/3] UefiCpuPkg/PiSmmCpu: Refine CR2 save/restore logic

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

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

> -----Original Message-----
> From: Ni, Ray
> Sent: Saturday, July 27, 2019 11:29 AM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Laszlo Ersek <lersek@redhat.com>;
> Vanguput, Narendra K <narendra.k.vanguput@intel.com>
> Subject: [PATCH 2/3] UefiCpuPkg/PiSmmCpu: Refine CR2 save/restore logic
> 
> Because IsStaticPageTableEnabled() is added for both IA32 and x64 build, the
> CR2 save/restore logic can be refined:
> 1. Remove arch specific SaveCr2() /  RestoreCr2() implementation; 2.
> Conditionally save and restore CR2 in SmiRendezvous().
> 
> Signed-off-by: Ray Ni <ray.ni@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Vanguput Narendra K <narendra.k.vanguput@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c   | 25 -------------------
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c      |  8 ++++--
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 22 ----------------
>  UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c    | 29 ----------------------
>  4 files changed, 6 insertions(+), 78 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> index 2a9af4b77d..cae23d6d1d 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> @@ -327,28 +327,3 @@ SetPageTableAttributes (
>    return ;
>  }
> 
> -/**
> -  This function returns with no action for 32 bit.
> -
> -  @param[out]  *Cr2  Pointer to variable to hold CR2 register value.
> -**/
> -VOID
> -SaveCr2 (
> -  OUT UINTN  *Cr2
> -  )
> -{
> -  return ;
> -}
> -
> -/**
> -  This function returns with no action for 32 bit.
> -
> -  @param[in]  Cr2  Value to write into CR2 register.
> -**/
> -VOID
> -RestoreCr2 (
> -  IN UINTN  Cr2
> -  )
> -{
> -  return ;
> -}
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index ef16997547..5d0124b368 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1575,7 +1575,9 @@ SmiRendezvous (
>    // when using on-demand paging for above 4G memory.
>    //
>    Cr2 = 0;
> -  SaveCr2 (&Cr2);
> +  if (!IsStaticPageTableEnabled ()) {
> +    Cr2 = AsmReadCr2 ();
> +  }
> 
>    //
>    // Call the user register Startup function first.
> @@ -1725,7 +1727,9 @@ Exit:
>    //
>    // Restore Cr2
>    //
> -  RestoreCr2 (Cr2);
> +  if (!IsStaticPageTableEnabled ()) {
> +    AsmWriteCr2 (Cr2);
> +  }
>  }
> 
>  /**
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> index 14b7676c16..5a97733def 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> @@ -1282,28 +1282,6 @@ IsStaticPageTableEnabled (
>    )
>  ;
> 
> -/**
> -  This function reads CR2 register when on-demand paging is enabled
> -  for 64 bit and no action for 32 bit.
> -
> -  @param[out]  *Cr2  Pointer to variable to hold CR2 register value.
> -**/
> -VOID
> -SaveCr2 (
> -  OUT UINTN  *Cr2
> -  );
> -
> -/**
> -  This function writes into CR2 register when on-demand paging is enabled
> -  for 64 bit and no action for 32 bit.
> -
> -  @param[in]  Cr2  Value to write into CR2 register.
> -**/
> -VOID
> -RestoreCr2 (
> -  IN UINTN  Cr2
> -  );
> -
>  /**
>    Schedule a procedure to run on the specified CPU.
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> index 18e3f9e08d..8259b01a95 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> @@ -1209,32 +1209,3 @@ SetPageTableAttributes (
>    return ;
>  }
> 
> -/**
> -  This function reads CR2 register when on-demand paging is enabled.
> -
> -  @param[out]  *Cr2  Pointer to variable to hold CR2 register value.
> -**/
> -VOID
> -SaveCr2 (
> -  OUT UINTN  *Cr2
> -  )
> -{
> -  if (!mCpuSmmStaticPageTable) {
> -    *Cr2 = AsmReadCr2 ();
> -  }
> -}
> -
> -/**
> -  This function restores CR2 register when on-demand paging is enabled.
> -
> -  @param[in]  Cr2  Value to write into CR2 register.
> -**/
> -VOID
> -RestoreCr2 (
> -  IN UINTN  Cr2
> -  )
> -{
> -  if (!mCpuSmmStaticPageTable) {
> -    AsmWriteCr2 (Cr2);
> -  }
> -}
> --
> 2.21.0.windows.1