From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: Re: [PATCH v2] x86/efi: always map first physical page into EFI pagetables Date: Fri, 27 Jan 2017 16:23:15 +0000 Message-ID: <20170127162315.GG31613@codeblueprint.co.uk> References: <20170127151248.GF31613@codeblueprint.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jiri Kosina Cc: Ard Biesheuvel , Waiman Long , Borislav Petkov , Laura Abbott , Vojtech Pavlik , Hanka Pavlikova , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-efi@vger.kernel.org On Fri, 27 Jan, at 04:39:59PM, Jiri Kosina wrote: > From: Jiri Kosina > > Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in > mixed-mode") stopped creating 1:1 mapping for all RAM in case of running > in native 64bit mode. > > It turns out though that there are 64bit EFI implementations in the wild > (this particular problem has been reported on Lenovo Yoga 710-11IKB) which > still make use of first physical page for their own private use even > though they explicitly mark it EFI_CONVENTIONAL_MEMORY in the memory map. > > In case there is no mapping for this particular frame in EFI pagetables, > as soon as firmware tries to make use of it, triple fault occurs and the > system reboots (in case of Yoga 710-11IKB this is very early during boot). > > Fix that by always mapping the first page of physical memory into EFI > pagetables. We're on a safe side, as trim_bios_range() will reserve the > first page and isolate it away from memory allocators anyway. > > Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the > regression on affected hardware, as commit ab72a27da ("x86/efi: > Consolidate region mapping logic") later made the first physical frame not > to be mapped anyway. > > Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode") > Cc: stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org # v4.8+ > Cc: Waiman Long > Cc: Borislav Petkov > Cc: Laura Abbott > Cc: Vojtech Pavlik > Reported-by: Hanka Pavlikova > Signed-off-by: Jiri Kosina > --- Thanks Jiri. Queued for v4.10-rc6.