Re: [PATCH] x86/boot: Don't use INC to set defaults

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

On Thu, Oct 3, 2024 at 3:58 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>
> __efi64_mb2_start() makes some bold assumptions about the efi_platform and
> skip_realmode booleans.  Set them to 1 explicitly, which is more robust.
>
> Make the comment a little more consice.
>
> No practical change.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> CC: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
> ---
>  xen/arch/x86/boot/head.S | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index d1856d8012c9..af776c201a15 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -279,14 +279,12 @@ __efi64_mb2_start:
>          pop     %rbx
>          pop     %rax
>
> -        /* We are on EFI platform and EFI boot services are available. */
> -        incb    efi_platform(%rip)
> -
>          /*
> -         * Disable real mode and other legacy stuff which should not
> -         * be run on EFI platforms.
> +         * efi_multiboot2_prelude() is happy that we're on EFI platform.  
> Skip
> +         * the BIOS initialisation path.
>           */
> -        incb    skip_realmode(%rip)
> +        movb    $1, efi_platform(%rip)
> +        movb    $1, skip_realmode(%rip)
>
>          /* Jump to trampoline_setup after switching CPU to x86_32 mode. */
>          lea     trampoline_setup(%rip),%r15
>
> base-commit: eb21ce14d709ef0c0030d0625028a4868c81126f

Reviewed-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>

I like _Bool !

Frediano