Re: [edk2-devel] [PATCH 03/10] OvmfPkg/ResetVector: add CreatePageTables4Level macro

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

On 2/22/24 12:54, Gerd Hoffmann wrote:
> Move code to create 4-level page tables to a nasm macro.
> No functional change.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 70 +++++++++++++----------
>  1 file changed, 39 insertions(+), 31 deletions(-)
> 
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index 378ba2feeb4f..14cc2c33aa3d 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -63,6 +63,44 @@ BITS    32
>      loop    .clearPageTablesMemoryLoop
>  %endmacro
>  
> +;
> +; Create page tables for 4-level paging
> +;
> +; Argument: upper 32 bits of the page table entries
> +;
> +%macro CreatePageTables4Level 1
> +    ;
> +    ; Top level Page Directory Pointers (1 * 512GB entry)
> +    ;
> +    mov     dword[PT_ADDR (0)], PT_ADDR (0x1000) + PAGE_PDE_DIRECTORY_ATTR
> +    mov     dword[PT_ADDR (4)], %1
> +
> +    ;
> +    ; Next level Page Directory Pointers (4 * 1GB entries => 4GB)
> +    ;
> +    mov     dword[PT_ADDR (0x1000)], PT_ADDR (0x2000) + PAGE_PDE_DIRECTORY_ATTR
> +    mov     dword[PT_ADDR (0x1004)], %1
> +    mov     dword[PT_ADDR (0x1008)], PT_ADDR (0x3000) + PAGE_PDE_DIRECTORY_ATTR
> +    mov     dword[PT_ADDR (0x100C)], %1
> +    mov     dword[PT_ADDR (0x1010)], PT_ADDR (0x4000) + PAGE_PDE_DIRECTORY_ATTR
> +    mov     dword[PT_ADDR (0x1014)], %1
> +    mov     dword[PT_ADDR (0x1018)], PT_ADDR (0x5000) + PAGE_PDE_DIRECTORY_ATTR
> +    mov     dword[PT_ADDR (0x101C)], %1
> +
> +    ;
> +    ; Page Table Entries (2048 * 2MB entries => 4GB)
> +    ;
> +    mov     ecx, 0x800
> +.pageTableEntriesLoop4Level:
> +    mov     eax, ecx
> +    dec     eax
> +    shl     eax, 21
> +    add     eax, PAGE_PDE_LARGEPAGE_ATTR
> +    mov     dword[ecx * 8 + PT_ADDR (0x2000 - 8)], eax
> +    mov     dword[(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], %1
> +    loop    .pageTableEntriesLoop4Level
> +%endmacro
> +
>  ;
>  ; Modified:  EAX, EBX, ECX, EDX
>  ;
> @@ -88,37 +126,7 @@ SetCr3ForPageTables64:
>  
>  ClearOvmfPageTables:
>      ClearOvmfPageTables
> -
> -    ;
> -    ; Top level Page Directory Pointers (1 * 512GB entry)
> -    ;
> -    mov     dword[PT_ADDR (0)], PT_ADDR (0x1000) + PAGE_PDE_DIRECTORY_ATTR
> -    mov     dword[PT_ADDR (4)], edx
> -
> -    ;
> -    ; Next level Page Directory Pointers (4 * 1GB entries => 4GB)
> -    ;
> -    mov     dword[PT_ADDR (0x1000)], PT_ADDR (0x2000) + PAGE_PDE_DIRECTORY_ATTR
> -    mov     dword[PT_ADDR (0x1004)], edx
> -    mov     dword[PT_ADDR (0x1008)], PT_ADDR (0x3000) + PAGE_PDE_DIRECTORY_ATTR
> -    mov     dword[PT_ADDR (0x100C)], edx
> -    mov     dword[PT_ADDR (0x1010)], PT_ADDR (0x4000) + PAGE_PDE_DIRECTORY_ATTR
> -    mov     dword[PT_ADDR (0x1014)], edx
> -    mov     dword[PT_ADDR (0x1018)], PT_ADDR (0x5000) + PAGE_PDE_DIRECTORY_ATTR
> -    mov     dword[PT_ADDR (0x101C)], edx
> -
> -    ;
> -    ; Page Table Entries (2048 * 2MB entries => 4GB)
> -    ;
> -    mov     ecx, 0x800
> -pageTableEntriesLoop:
> -    mov     eax, ecx
> -    dec     eax
> -    shl     eax, 21
> -    add     eax, PAGE_PDE_LARGEPAGE_ATTR
> -    mov     [ecx * 8 + PT_ADDR (0x2000 - 8)], eax
> -    mov     [(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], edx
> -    loop    pageTableEntriesLoop
> +    CreatePageTables4Level edx
>  
>      ; Clear the C-bit from the GHCB page if the SEV-ES is enabled.
>      OneTimeCall   SevClearPageEncMaskForGhcbPage

Nice.

"--color-moved=zebra" is really useful for viewing this patch.

Same comment on the ".pageTableEntriesLoop4Level" label name as under
patch#2: can we use "..@pageTableEntriesLoop4Level"?

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



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