From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH][v8] PM / hibernate: Verify the consistent of e820 memory map by md5 value Date: Sun, 28 Aug 2016 18:36:59 +0200 Message-ID: <20160828163659.GA19306@amd> References: <1472402140-959-1-git-send-email-yu.c.chen@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1472402140-959-1-git-send-email-yu.c.chen@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Chen Yu Cc: linux-pm@vger.kernel.org, "Rafael J. Wysocki" , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Lee@amd.karlin.mff.cuni.cz, Chun-Yi , Borislav Petkov List-Id: linux-pm@vger.kernel.org On Mon 2016-08-29 00:35:40, Chen Yu wrote: > On some platforms, there is occasional panic triggered when trying to > resume from hibernation, a typical panic looks like: > > "BUG: unable to handle kernel paging request at ffff880085894000 > IP: [] load_image_lzo+0x8c2/0xe70" > > This is because e820 map has been changed by BIOS across > hibernation, and one of the page frames from first kernel > is right located in second kernel's unmapped region, so panic > comes out when accessing unmapped kernel address. > > In order to expose this issue earlier, the md5 hash of e820 map > is passed from suspend kernel to resume kernel, and the system will > trigger panic once it finds the md5 value of previous kernel is not > the same as current resume kernel. > > Note: > 1. Without this patch applied, it is possible that BIOS has > provided an inconsistent memory map, but the resume kernel is still > able to restore the image anyway(e.g., E820_RAM region is the subset > of the previous one), although the system might be unstable. So this > patch tries to treat any inconsistent e820 as illegal. > > 2. Another case is, this patch replies on comparing the e820_saved, but > currently the e820_save might not be strictly the same across > hibernation, even if BIOS has provided consistent e820 map - In > theory mptable might modify the BIOS-provided e820_saved dynamically > in early_reserve_e820_mpc_new, which would allocate a buffer from > E820_RAM, and marks it from E820_RAM to E820_RESERVED). > This is a potential and rare case we need to deal with in OS in > the future. > > Suggested-by: Pavel Machek > Suggested-by: Rafael J. Wysocki > Cc: Lee, Chun-Yi > Cc: Borislav Petkov > Signed-off-by: Chen Yu Acked-by: Pavel Machek You might want to verify that panic is actually visible on affected platform. Thanks for your patience ;-). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html