On Saturday, October 22, 2016 11:03:02 AM joeyli wrote: > Hi Chen Yu, > > On Thu, Oct 20, 2016 at 04:14:52PM +0800, 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: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70" > > > > Investigation carried out by Lee Chun-Yi shows that this is because > > e820 map has been changed by BIOS across hibernation, and one > > of the page frames from suspend kernel is right located in restore > > 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 restore kernel, and the restore > > kernel will terminate the resume process once it finds the md5 > > hash are not the same. > > > > As the format of image header has been modified, the magic number > > should also be adjusted as kernels with the same RESTORE_MAGIC have > > to use the same header format and interpret all of the fields in > > it in the same way. > > > > If the suspend kernel is built without md5 support, and the restore > > kernel has md5 support, then the latter will bypass the check process. > > Vice versa the restore kernel will bypass the check if it does not > > support md5 operation. > > > > 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 superset > > 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 <pa...@ucw.cz> > > Suggested-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > Cc: Pavel Machek <pa...@ucw.cz> > > Cc: Lee Chun-Yi <j...@suse.com> > > Cc: Borislav Petkov <b...@alien8.de> > > Cc: Len Brown <len.br...@intel.com> > > Cc: Denys Vlasenko <dvlas...@redhat.com> > > Cc: Dan Williams <dan.j.willi...@intel.com> > > Signed-off-by: Chen Yu <yu.c.c...@intel.com> > > Please feel free to add: > Reviewed-by: Lee, Chun-Yi <j...@suse.com>
Applied (with the tag above). Thanks, Rafael
