Hi Narendra,
With this implementation, you have moved the save/restore
location to a module global variable. The name should be
prefixed with 'm' to make that clear.
mCr2
I do not think using a module global is MP safe.
The current implementation uses a local on the stack that
is MP safe because each CPU has its own stack.
Mike
> -----Original Message-----
> From: edk2-devel [mailto:[email protected]]
> On Behalf Of nkvangup
> Sent: Friday, March 22, 2019 11:50 AM
> To: [email protected]
> Cc: Yao, Jiewen <[email protected]>; Dong, Eric
> <[email protected]>; Laszlo Ersek <[email protected]>
> Subject: [edk2] [PATCH v5] 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.
> This is not a bug but to have better improvement of code.
>
> Patch5 is updated with separate functions for Save and
> Restore of CR2
> based on review feedback.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Vanguput Narendra K
> <[email protected]>
> Cc: Eric Dong <[email protected]>
> Cc: Ray Ni <[email protected]>
> Cc: Laszlo Ersek <[email protected]>
> Cc: Yao Jiewen <[email protected]>
> ---
> UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c | 22
> ++++++++++++++++++++++
> UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 9 +++++---
> -
> UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 16
> ++++++++++++++++
> UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c | 28
> ++++++++++++++++++++++++++++
> 4 files changed, 71 insertions(+), 4 deletions(-)
>
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> index b734a1ea8c..3750332ca8 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
> @@ -316,3 +316,25 @@ SetPageTableAttributes (
>
> return ;
> }
> +
> +/**
> + This function returns with no action for 32 bit.
> +**/
> +VOID
> +SaveCr2 (
> + VOID
> + )
> +{
> +// Do Nothing
> +}
> +
> +/**
> + This function returns with no action for 32 bit.
> +**/
> +VOID
> +RestoreCr2 (
> + VOID
> + )
> +{
> +// Do Nothing
> +}
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index 3b0b3b52ac..6a5736a3eb 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1107,14 +1107,14 @@ SmiRendezvous (
> BOOLEAN IsBsp;
> BOOLEAN BspInProgress;
> UINTN Index;
> - UINTN Cr2;
>
> ASSERT(CpuIndex < mMaxNumberOfCpus);
>
> //
> - // Save Cr2 because Page Fault exception in SMM may
> override its value
> + // Save Cr2 because Page Fault exception in SMM may
> override its value,
> + // when using on-demand paging for above 4G memory.
> //
> - Cr2 = AsmReadCr2 ();
> + SaveCr2 ();
>
> //
> // Perform CPU specific entry hooks
> @@ -1253,10 +1253,11 @@ SmiRendezvous (
>
> Exit:
> SmmCpuFeaturesRendezvousExit (CpuIndex);
> +
> //
> // Restore Cr2
> //
> - AsmWriteCr2 (Cr2);
> + RestoreCr2 ();
> }
>
> /**
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> index 84efb22981..71a8c13960 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> @@ -1243,4 +1243,20 @@ EFIAPI
> PiSmmCpuSmiEntryFixupAddress (
> );
>
> +/**
> + This function saves CR2 register for 64 bit and no
> action for 32 bit.
> +**/
> +VOID
> +SaveCr2 (
> + VOID
> + );
> +
> +/**
> + This function restores CR2 register for 64 bit and no
> action for 32 bit.
> +**/
> +VOID
> +RestoreCr2 (
> + VOID
> + );
> +
> #endif
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> index 2c77cb47a4..76a30de171 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> @@ -22,6 +22,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS
> OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> LIST_ENTRY mPagePool =
> INITIALIZE_LIST_HEAD_VARIABLE (mPagePool);
> BOOLEAN m1GPageTableSupport
> = FALSE;
> BOOLEAN
> mCpuSmmStaticPageTable;
> +UINTN Cr2 = 0;
>
> /**
> Disable CET.
> @@ -1053,3 +1054,30 @@ SetPageTableAttributes (
>
> return ;
> }
> +
> +/**
> + This function saves CR2 register.
> +**/
> +VOID
> +SaveCr2 (
> + VOID
> + )
> +{
> + if (!mCpuSmmStaticPageTable) {
> + Cr2 = AsmReadCr2 ();
> + }
> +}
> +
> +/**
> + This function restores CR2 register.
> +**/
> +VOID
> +RestoreCr2 (
> + VOID
> + )
> +{
> + if ((!mCpuSmmStaticPageTable) && (Cr2 != 0)) {
> + AsmWriteCr2 (Cr2);
> + Cr2 = 0;
> + }
> +}
> --
> 2.16.2.windows.1
>
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