Re: [PATCH][v8] PM / hibernate: Verify the consistent of e820 memory map by md5 value

[Chen Yu <yu.c.chen@intel.com>]

Hi Pavel,
On Thu, Sep 08, 2016 at 11:15:52PM +0200, Pavel Machek wrote:
> On Tue 2016-08-30 13:54:44, Rafael J. Wysocki wrote:
> > On Tuesday, August 30, 2016 04:35:05 PM joeyli wrote:
> > > On Mon, Aug 29, 2016 at 03:41:23PM +0200, Borislav Petkov wrote:
> > > > On Mon, Aug 29, 2016 at 09:15:00AM +0200, Pavel Machek wrote:
> > > > > Sounds about as easy as hot unplugging arbitrary memory address. IOW
> > > > > "not easy".
> > > > 
> > > > Regardless, forcibly panicking the system more is still the wrong
> > > > approach IMO.
> > > > 
> > > > Instead, I'd try to issue a big fat warning that BIOS corrupts E820 and
> > > > that the user should disable hibernation on that box and never ever
> > > > enable it again.
> > > > 
> > > > After that, the kernel should *disable* hibernation for the current boot
> > > > so any further hibernation runs don't even happen. Maybe even taint
> > > > itself.
> > > >
> > > 
> > > I support this idea to disable hibernation when kernel detected e820 layout
> > > was changed by BIOS. If system resume luckily then kernel should warn to user
> > > and refuse to hibernate again. User must to know that's better to reboot
> > > system when he saw the warning message after lucky resume.
> > > 
> > > Not just BIOS doesn't fix e820 layout. There have some machines doesn't provide
> > > _S4_ function, so the hibernation fallbacks to "shutdown" mode because "platform"
> > > mode unavailable. In this situation, user is just lucky to run the hibernation.
> > > Kernel should warn to user and disable hibernation when detected e820 layout
> > > changed.
> > 
> > Well, please see my reply to Boris.
> > 
> > Pavel is right that running after detecting an e820 mismatch is generally risky,
> > so why don't we shut down the system (but try to do that cleanly instead of
> > causing it to panic right away) on an e820 mismatch?
> 
> I don't think that's good idea.
> 
> Anything involving userspace is risky at that point, and clean
> shutdown means a _lot_ of userspace.
> 
> We know the filesystems are reasonably clean as we sync-ed
> them; I believe right solution is to panic -- on-disk state is pretty
> good and we don't want to do anything risky.
>
OK, we tried a milder solution that doesn't shutdown the system in the
latest version, which terminates the restore process if a mismatch is found
(hope people would be happy with that one :)
Here's the patch link per yours and Rafael's last comments on the old patch,
and I'm still doing some small adjustment and will send a newer one but it
is approximately similar to the following link:

https://patchwork.kernel.org/patch/9310497/