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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Oct 03, 2024 at 04:42:23PM +0100, Frediano Ziglio wrote:
> 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>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks, Roger.