Re: [PATCH v6 2/3] x86/boot: Rewrite EFI/MBI2 code partly in C

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

On Tue, Oct 1, 2024 at 9:52 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 01.10.2024 10:35, Frediano Ziglio wrote:
> > On Mon, Sep 30, 2024 at 4:51 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >> On 26.09.2024 11:21, Frediano Ziglio wrote:
> >>> @@ -243,7 +234,7 @@ __efi64_mb2_start:
> >>>          /*
> >>>           * Initialize BSS (no nasty surprises!).
> >>>           * It must be done earlier than in BIOS case
> >>> -         * because efi_multiboot2() touches it.
> >>> +         * because efi_multiboot2_prelude() touches it.
> >>>           */
> >>>          mov     %eax, %edx
> >>
> >> I think this MOV wants to gain a comment, now that ...
> >>
> >>>          lea     __bss_start(%rip), %edi
> >>> @@ -252,36 +243,30 @@ __efi64_mb2_start:
> >>>          shr     $3, %ecx
> >>>          xor     %eax, %eax
> >>>          rep stosq
> >>> -        mov     %edx, %eax
> >>
> >> ... this one's going away.
> >>
> >
> > What about
> >
> > diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> > index 89b5e2af88..6fa6ea93e5 100644
> > --- a/xen/arch/x86/boot/head.S
> > +++ b/xen/arch/x86/boot/head.S
> > @@ -231,12 +231,14 @@ __efi64_mb2_start:
> >          */
> >         and     $~15, %rsp
> >
> > +       /* Move away magic number, we need it later but we need to use %eax 
> > */
> > +        mov     %eax, %edx
> > +
> >         /*
> >          * Initialize BSS (no nasty surprises!).
> >          * It must be done earlier than in BIOS case
> >          * because efi_multiboot2_prelude() touches it.
> >          */
> > -        mov     %eax, %edx
> >         lea     __bss_start(%rip), %edi
> >         lea     __bss_end(%rip), %ecx
> >         sub     %edi, %ecx
> >
> > ??
>
> Fine with me. Maybe s/Move away/Save"?
>
> Jan

Done.

One last though. Do you think I should now rename
xen/arch/x86/efi/parse-mbi2.c file ?

Frediano