Re: [PATCH 1/3] x86/boot: Initialise BSS as soon as possible

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

On Sun, Sep 15, 2024 at 7:20 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 10.09.2024 18:16, Frediano Ziglio wrote:
> > --- a/xen/arch/x86/boot/head.S
> > +++ b/xen/arch/x86/boot/head.S
> > @@ -231,6 +231,27 @@ __efi64_mb2_start:
> >          /* VGA is not available on EFI platforms. */
> >          movl   $0,vga_text_buffer(%rip)
> >
> > +        /*
> > +         * Align the stack as UEFI spec requires. Keep it aligned
> > +         * before efi_multiboot2() call by pushing/popping even
> > +         * numbers of items on it.
> > +         */
> > +        and     $~15,%rsp
>
> You don't use the stack below, so it's not clear if/why this needs
> moving. If it does, please add the missing blank after the comma
> (like you nicely do everywhere else).
>

Fixed the blank. The reason is more clear if you look at the last
commit in the series, at least for the EFI part. For the BIOS/PVH part
is less clear, but the rationale is the same. The commit came from a
larger series where BIOS/PVH is mainly written in C so there is more
clear.

> Apart from this there's the question on the precise placement of
> the calls - see respective comment on patch 2 (which I needed to
> look at first to have an opinion here).
>

I think you removed too much context, not clear what code you are
referring to, last hunk above is an "and" instruction.

> Jan

Frediano