Re: [edk2-devel] [PATCH v2 3/5] OvmfPkg/ResetVector: improve page table flag names

["Pedro Falcato" <pedro.falcato@gmail.com>]

On Tue, Jan 30, 2024 at 12:32 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> Add comments, rename some of the PAGE_* flags and combined attributes.
> Specifically use "LARGEPAGE" instead of "2M" because that bit is used
> for both 2M and 1G large pages.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 39 +++++++++++++----------
>  1 file changed, 22 insertions(+), 17 deletions(-)
>
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index 317cad430f29..6fec6f2beeea 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -10,6 +10,7 @@
>
>  BITS    32
>
> +; common for all levels
>  %define PAGE_PRESENT            0x01
>  %define PAGE_READ_WRITE         0x02
>  %define PAGE_USER_SUPERVISOR    0x04
> @@ -17,25 +18,29 @@ BITS    32
>  %define PAGE_CACHE_DISABLE     0x010
>  %define PAGE_ACCESSED          0x020
>  %define PAGE_DIRTY             0x040
> -%define PAGE_PAT               0x080
>  %define PAGE_GLOBAL           0x0100
> -%define PAGE_2M_MBO            0x080
> -%define PAGE_2M_PAT          0x01000
> +
> +; page table entries (level 1)
> +%define PAGE_PTE_PAT           0x080
> +
> +; page directory entries (level 2+)
> +%define PAGE_PDE_LARGEPAGE     0x080
> +%define PAGE_PDE_PAT         0x01000
>
>  %define PAGE_4K_PDE_ATTR (PAGE_ACCESSED + \
>                            PAGE_DIRTY + \
>                            PAGE_READ_WRITE + \
>                            PAGE_PRESENT)
>
> -%define PAGE_2M_PDE_ATTR (PAGE_2M_MBO + \
> -                          PAGE_ACCESSED + \
> -                          PAGE_DIRTY + \
> -                          PAGE_READ_WRITE + \
> -                          PAGE_PRESENT)
> +%define PAGE_PDE_LARGEPAGE_ATTR (PAGE_PDE_LARGEPAGE + \
> +                                 PAGE_ACCESSED + \
> +                                 PAGE_DIRTY + \
> +                                 PAGE_READ_WRITE + \
> +                                 PAGE_PRESENT)
>
> -%define PAGE_PDP_ATTR (PAGE_ACCESSED + \
> -                       PAGE_READ_WRITE + \
> -                       PAGE_PRESENT)
> +%define PAGE_PDE_DIRECTORY_ATTR (PAGE_ACCESSED + \
> +                                 PAGE_READ_WRITE + \
> +                                 PAGE_PRESENT)
>
>  %define TDX_BSP         1
>  %define TDX_AP          2
> @@ -84,19 +89,19 @@ clearPageTablesMemoryLoop:
>      ;
>      ; Top level Page Directory Pointers (1 * 512GB entry)
>      ;
> -    mov     dword[PT_ADDR (0)], PT_ADDR (0x1000) + PAGE_PDP_ATTR
> +    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_PDP_ATTR
> +    mov     dword[PT_ADDR (0x1000)], PT_ADDR (0x2000) + PAGE_PDE_DIRECTORY_ATTR

Technically, if we want to be pedantic, these are PDPTEs (or PDPs I
guess), so PDE is misleading here.

-- 
Pedro


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