On Mon, Jun 10, 2024 at 2:24 PM Ard Biesheuvel <ardb+git@xxxxxxxxxx> wrote: > From: Ard Biesheuvel <ardb@xxxxxxxxxx> > > EFI runtime services are remapped into the lower 1 GiB of virtual > address space at boot, so they are guaranteed to be able to co-exist > with the kernel virtual mappings without the need to allocate space for > them in the kernel's vmalloc region, which is rather small. > > This means those mappings are covered by TTBR0 when LPAE PAN is enabled, > and so 'user' access must be enabled while such calls are in progress. > > To avoid the need to refactor the code that is shared between ARM, arm64 > and other EFI architectures, fold this into efi_set_pgd(). Given that > EFI runtime services are serialized and not pre-emptible, storing the > flags into a global variable is reasonable here - efi_set_pgd() calls > will always occur in pairs on a single CPU. > > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Makes sense to me! Thanks for looking into this. Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx> Yours, Linus Walleij
