On Tue, Dec 06, 2022 at 11:17:20AM +0000, Andrew Cooper wrote: > On 06/12/2022 04:33, Demi Marie Obenour wrote: > > This makes the code much easier to understand, and avoids problems if > > Xen's PAT ever changes in the future. > > > > Signed-off-by: Demi Marie Obenour <[email protected]> > > --- > > xen/common/efi/boot.c | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c > > index > > 8e880fe30c7541a202dec3e665300d6549953aa3..260997b251b09dae4b48c1b1db665778e02d760a > > 100644 > > --- a/xen/common/efi/boot.c > > +++ b/xen/common/efi/boot.c > > @@ -1746,21 +1746,21 @@ void __init efi_init_memory(void) > > if ( desc->Attribute & EFI_MEMORY_WB ) > > /* nothing */; > > This is an implicit 0 case which wants changing to _PAGE_WB.
Good catch! I will make this change in v2, but I also will add BUILD_BUG_ON(_PAGE_WB), as at least Linux assumes that _PAGE_WB is 0. > > else if ( desc->Attribute & EFI_MEMORY_WT ) > > - prot |= _PAGE_PWT | MAP_SMALL_PAGES; > > + prot |= _PAGE_WT | MAP_SMALL_PAGES; > > else if ( desc->Attribute & EFI_MEMORY_WC ) > > - prot |= _PAGE_PAT | MAP_SMALL_PAGES; > > + prot |= _PAGE_WC | MAP_SMALL_PAGES; > > else if ( desc->Attribute & (EFI_MEMORY_UC | EFI_MEMORY_UCE) ) > > - prot |= _PAGE_PWT | _PAGE_PCD | MAP_SMALL_PAGES; > > + prot |= _PAGE_UC | MAP_SMALL_PAGES; > > else if ( efi_bs_revision >= EFI_REVISION(2, 5) && > > (desc->Attribute & EFI_MEMORY_WP) ) > > - prot |= _PAGE_PAT | _PAGE_PWT | MAP_SMALL_PAGES; > > + prot |= _PAGE_WP | MAP_SMALL_PAGES; > > Unrelated to the transformation. I'm unconvinced about the correctness > of using MAP_SMALL_PAGES here. There's nothing wrong with large pages > of reduced cache-ability, and the framebuffer is going to live in one of > these regions, probably a WC one... I can make that a separate patch. -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab
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