Re: [edk2-devel] [PATCH 10/10] OvmfPkg/ResetVector: wire up 5-level paging for SEV

["Laszlo Ersek" <lersek@redhat.com>]

On 2/22/24 12:54, Gerd Hoffmann wrote:
> Removes the GetSevCBitMaskAbove31 OneTimeCall because we need that twice
> (for 4-level and 5-level paging).  Open code the single instruction left
> in that function instead.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  OvmfPkg/ResetVector/Ia32/AmdSev.asm       |  8 --------
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 14 +++++++++++++-
>  2 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
> index 9063ce1080d3..d1e5e8dfae71 100644
> --- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
> +++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
> @@ -191,14 +191,6 @@ pageTableEntries4kLoop:
>  SevClearPageEncMaskForGhcbPageExit:
>      OneTimeCallRet SevClearPageEncMaskForGhcbPage
>  
> -; Get the C-bit mask above 31.
> -; Modified: EDX
> -;
> -; The value is returned in the EDX
> -GetSevCBitMaskAbove31:
> -    mov       edx, dword[SEV_ES_WORK_AREA_ENC_MASK + 4]
> -    OneTimeCallRet GetSevCBitMaskAbove31
> -
>  %endif
>  
>  ; Check if Secure Encrypted Virtualization (SEV) features are enabled.
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index 6e2063430802..55664fa64f62 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -243,11 +243,23 @@ SevInit:
>      ; SEV workflow
>      ;
>      ClearOvmfPageTables
> +%if PG_5_LEVEL
> +    Check5LevelPaging Sev4Level
>      ; If SEV is enabled, the C-bit position is always above 31.
>      ; The mask will be saved in the EDX and applied during the
>      ; the page table build below.
> -    OneTimeCall   GetSevCBitMaskAbove31
> +    mov edx, dword[SEV_ES_WORK_AREA_ENC_MASK + 4]
> +    CreatePageTables5Level edx
> +    Enable5LevelPaging
> +    jmp SevCommon
> +Sev4Level:
> +%endif
> +    ; If SEV is enabled, the C-bit position is always above 31.
> +    ; The mask will be saved in the EDX and applied during the
> +    ; the page table build below.
> +    mov edx, dword[SEV_ES_WORK_AREA_ENC_MASK + 4]
>      CreatePageTables4Level edx
> +SevCommon:
>      ; Clear the C-bit from the GHCB page if the SEV-ES is enabled.
>      OneTimeCall   SevClearPageEncMaskForGhcbPage
>      OneTimeCall   SevClearVcHandlerAndStack

This patch looks fine to me (especially the SevCommon label), but can
you please reimplement GetSevCBitMaskAbove31 as a macro, rather than
open-coding the

  mov edx, dword[SEV_ES_WORK_AREA_ENC_MASK + 4]

instruction?

Thanks!
Laszlo



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