Re: efi boot failures due to PTI with 32 bit builds and Intel CPUs

From: Joerg Roedel
Date: Thu Aug 30 2018 - 14:46:44 EST

On Thu, Aug 30, 2018 at 11:21:49AM -0700, Linus Torvalds wrote:
> On Thu, Aug 30, 2018 at 11:08 AM Joerg Roedel <jroedel@xxxxxxx> wrote:
> >
> > Without a mapped GDT the #PF and #DF handlers also can't be started, so
> > the machine triple-faults. Below diff fixes it for me, I'll send a
> > proper patch tomorrow.
> Hmm. Is there any reason why this code doesn't just use
> load_fixmap_gdt(0);

No idea, probably the function didn't exist when the code was written?
I can change that when writing the patch.

> and shouldn't it do it after loading the new %cr3?

That seems more robust, yes. No sure if the old %cr3
(initial_page_table) has the fixmap gdt mapped at all.