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SubjectRe: [tip:x86/boot] x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G
On Tue, Feb 13, 2018 at 10:43:56AM +0100, Ingo Molnar wrote:
>
> * Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> > On Tue, Feb 13, 2018 at 12:41:22AM -0800, Andrei Vagin wrote:
> > > On Tue, Feb 13, 2018 at 11:08:16AM +0300, Kirill A. Shutemov wrote:
> > > > On Mon, Feb 12, 2018 at 10:51:56PM -0800, Andrei Vagin wrote:
> > > > > Hi Kirill,
> > > > >
> > > > > Something is wrong in this patch.
> >
> > Could you please check if this makes a difference?
> >
> > diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> > index 70b30f2bc9e0..99a0e7993252 100644
> > --- a/arch/x86/boot/compressed/head_64.S
> > +++ b/arch/x86/boot/compressed/head_64.S
> > @@ -332,7 +332,7 @@ ENTRY(startup_64)
> >
> > /* Make sure we have GDT with 32-bit code segment */
> > leaq gdt(%rip), %rax
> > - movl %eax, gdt64+2(%rip)
> > + movq %rax, gdt64+2(%rip)
> > lgdt gdt64(%rip)
>
> There's another suspicious looking pattern as well:
>
> leaq startup_32(%rip), %rax
> movl %eax, BP_code32_start(%rsi)
> ...
> movl BP_code32_start(%esi), %eax
> leaq startup_64(%rax), %rax
> ...

code32_start is 4-byte field as described in the boot protocol, so the
truncation is intentional I think.

--
Kirill A. Shutemov

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