[PATCH v2 2/2] x86/efi: Apply EFI Memory Attributes after kexec

[Dave Young]

Hi,

On Wed, 13 Nov 2024 at 02:53, Nicolas Saenz Julienne <nsaenz at amazon.com> wrote:
>
> Kexec bypasses EFI's switch to virtual mode. In exchange, it has its own
> routine, kexec_enter_virtual_mode(), which replays the mappings made by
> the original kernel. Unfortunately, that function fails to reinstate
> EFI's memory attributes, which would've otherwise been set after
> entering virtual mode. Remediate this by calling
> efi_runtime_update_mappings() within kexec's routine.

In the function __map_region(), there are playing with the flags
similar to the efi_runtime_update_mappings though it looks a little
different.  Is this extra callback really necessary?

Have you seen a real bug happened?

>
> Cc: stable at vger.kernel.org
> Fixes: 18141e89a76c ("x86/efi: Add support for EFI_MEMORY_ATTRIBUTES_TABLE")
> Signed-off-by: Nicolas Saenz Julienne <nsaenz at amazon.com>
>
> ---
>
> Notes:
> - Tested with QEMU/OVMF.
>
>  arch/x86/platform/efi/efi.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 375ebd78296a..a7ff189421c3 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -765,6 +765,7 @@ static void __init kexec_enter_virtual_mode(void)
>
>         efi_sync_low_kernel_mappings();
>         efi_native_runtime_setup();
> +       efi_runtime_update_mappings();
>  #endif
>  }
>
> --
> 2.40.1
>
>
Thanks
Dave