Re: [edk2-devel] [PATCH v2 08/10] OvmfPkg/ResetVector: wire up 5-level paging for TDX

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

On 3/1/24 08:44, Gerd Hoffmann wrote:
> BSP workflow is quite simliar to the non-coco case.
> 
> TDX_WORK_AREA_PGTBL_READY is used to record the paging mode:
>   1 == 4-level paging
>   2 == 5-level paging
> 
> APs will look at TDX_WORK_AREA_PGTBL_READY to figure whenever
> they should enable 5-level paging or not.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  OvmfPkg/ResetVector/Ia32/IntelTdx.asm     | 13 ++++++++++++-
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 16 ++++++++++++++++
>  2 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/OvmfPkg/ResetVector/Ia32/IntelTdx.asm b/OvmfPkg/ResetVector/Ia32/IntelTdx.asm
> index c6b86019dfb9..7d775591a05b 100644
> --- a/OvmfPkg/ResetVector/Ia32/IntelTdx.asm
> +++ b/OvmfPkg/ResetVector/Ia32/IntelTdx.asm
> @@ -179,7 +179,7 @@ InitTdx:
>  ;
>  ; Modified:  EAX, EDX
>  ;
> -; 0-NonTdx, 1-TdxBsp, 2-TdxAps
> +; 0-NonTdx, 1-TdxBsp, 2-TdxAps, 3-TdxAps5Level
>  ;
>  CheckTdxFeaturesBeforeBuildPagetables:
>      xor     eax, eax
> @@ -200,6 +200,17 @@ TdxPostBuildPageTables:
>      mov     byte[TDX_WORK_AREA_PGTBL_READY], 1
>      OneTimeCallRet TdxPostBuildPageTables
>  
> +%if PG_5_LEVEL
> +
> +;
> +; Set byte[TDX_WORK_AREA_PGTBL_READY] to 2
> +;
> +TdxPostBuildPageTables5Level:
> +    mov     byte[TDX_WORK_AREA_PGTBL_READY], 2
> +    OneTimeCallRet TdxPostBuildPageTables5Level
> +
> +%endif
> +
>  ;
>  ; Check if TDX is enabled
>  ;
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index e15945da0476..b922c845f297 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -44,6 +44,7 @@ BITS    32
>  
>  %define TDX_BSP         1
>  %define TDX_AP          2
> +%define TDX_AP_5_LEVEL  3
>  
>  ;
>  ; For OVMF, build some initial page tables at
> @@ -214,7 +215,14 @@ SetCr3ForPageTables64:
>      je        TdxBspInit
>      cmp       eax, TDX_AP
>      je        SetCr3
> +%if PG_5_LEVEL
> +    cmp       eax, TDX_AP_5_LEVEL
> +    jne       CheckForSev
> +    Enable5LevelPaging
> +    jmp       SetCr3
> +%endif
>  
> +CheckForSev:
>      ; Check whether the SEV is active and populate the SevEsWorkArea
>      OneTimeCall   CheckSevFeatures
>      cmp       byte[WORK_AREA_GUEST_TYPE], 1

Minor nit: we don't neet the "CheckForSev:" jump label at all if
PG_5_LEVEL is absent, so the "CheckForSev:" label definition should
still be in the "%if PG_5_LEVEL" scope.

(My proposal under v1 patch#6 was:

%if PG_5_LEVEL
    cmp       eax, TDX_AP_5_LEVEL
    jne       CheckForSev
    Enable5LevelPaging
    jmp       SetCr3
CheckForSev:
%endif

)

Did you place the "CheckForSev:" label intentionally outside of the %if
scope? If it was intentional, then I'm OK with it.

If it was unintended / an oversight, then next question: do you want me
to move the label into the %if's scope for you, upon merge? Or do you
like it better as written in your patch, after all?

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo




> @@ -253,6 +261,14 @@ TdxBspInit:
>      ; TDX BSP workflow
>      ;
>      ClearOvmfPageTables
> +%if PG_5_LEVEL
> +    Check5LevelPaging Tdx4Level
> +    CreatePageTables5Level 0
> +    OneTimeCall TdxPostBuildPageTables5Level
> +    Enable5LevelPaging
> +    jmp SetCr3
> +Tdx4Level:
> +%endif
>      CreatePageTables4Level 0
>      OneTimeCall TdxPostBuildPageTables
>      jmp SetCr3



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#116248): https://edk2.groups.io/g/devel/message/116248
Mute This Topic: https://groups.io/mt/104660117/7686176
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io]
-=-=-=-=-=-=-=-=-=-=-=-