Re: [Xen-devel] [PATCH v2 6/6] x86/boot: Do not use trampoline for no-real-mode boot paths

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.08.2019 17:25, David Woodhouse wrote:
> On Mon, 2019-08-12 at 12:55 +0200, Jan Beulich wrote:
> > On 09.08.2019 17:02, David Woodhouse wrote:
> > > @@ -97,7 +100,7 @@ GLOBAL(trampoline_realmode_entry)
> > >           cld
> > >           cli
> > >           lidt    trampsym(idt_48)
> > > -        lgdt    trampsym(gdt_48)
> > > +        lgdtl   trampsym(gdt_48)
> > Stray / unrelated change (and if needed, then also for lidt)?
> The difference between 16bit l.dt and 32-bit l.dtl is that the former
> only loads 24 bits of the actual table address (trampoline_gdt in this
> case).
>
> Thus, when trampoline_gdt is being used in-place, as it is during early
> boot, and *if* the Xen image is loaded higher than 16MiB, lgdt doesn't
> work. That's half a day of my life I want back.
But isn't this an issue even independent of your series? I.e. doesn't
this want to be fixed in a separate (to be backported) patch?

Jan

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