Re: [edk2-devel] [PATCH 1/3] MdeModulePkg: fix PcdUse5LevelPageTable assert

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

On 1/29/24 13:01, Gerd Hoffmann wrote:
> PcdUse5LevelPageTable documentation says:
> 
>   Indicates if 5-Level Paging will be enabled in long mode. 5-Level
>   Paging will not be enabled when the PCD is TRUE but CPU doesn't support
>   5-Level Paging.
> 
> So running in 4-level paging mode with PcdUse5LevelPageTable=TRUE is
> possible.  The only invalid combination is 5-level paging being active
> with PcdUse5LevelPageTable=FALSE.
> 
> Fix the ASSERT accordingly.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> index 980c2002d4f5..1d240e95966e 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> @@ -745,7 +745,9 @@ CreateIdentityMappingPageTables (
>      //
>      Cr4.UintN         = AsmReadCr4 ();
>      Page5LevelSupport = (Cr4.Bits.LA57 != 0);
> -    ASSERT (PcdGetBool (PcdUse5LevelPageTable) == Page5LevelSupport);
> +    if (Page5LevelSupport) {
> +      ASSERT (PcdGetBool (PcdUse5LevelPageTable));
> +    }
>    } else {
>      //
>      // If cpu runs in 32bit protected mode PEI, Page table Level in DXE is decided by PCD and feature capability.

FWIW, my observation at [1] was not that the PCD was incorrectly named -- I noted that the *local variable* "Page5LevelSupport" was a misnomer.

[1] http://mid.mail-archive.com/640e533e-5252-32da-c155-a25e3065eb78@redhat.com
    https://edk2.groups.io/g/devel/message/114318

I proposed "Page5LevelEnabled" instead.

But, it's not a show-stopper in any case. (I was a bit surprised to see the PCD rename in v2, but that would also have been an improvement.)

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



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