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Date: Thu, 30 Aug 2018 12:24:24 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Joerg Roedel <jroedel@...e.de> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Michal Hocko <mhocko@...e.com>, Andi Kleen <ak@...ux.intel.com>, the arch/x86 maintainers <x86@...nel.org>, Dave Hansen <dave.hansen@...el.com>, Pavel Machek <pavel@....cz> Subject: Re: efi boot failures due to PTI with 32 bit builds and Intel CPUs On Thu, Aug 30, 2018 at 08:46:39PM +0200, Joerg Roedel wrote: > 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@...e.de> 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. All three variants (hardcoded, call load_fixmap_gdt(0) first, call load_fixmap_gdt(0) after load_cr3()) work for me. Feel free to add Tested-by: Guenter Roeck <linux@...ck-us.net> when you submit the patch. Thanks a lot for tracking this down! Guenter
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