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

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Message-ID: <6348002.9YHCcajBsl@vostro.rjw.lan>
Date:   Tue, 30 Aug 2016 13:54:44 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     joeyli <jlee@...e.com>
Cc:     Borislav Petkov <bp@...en8.de>, Pavel Machek <pavel@....cz>,
        Chen Yu <yu.c.chen@...el.com>, linux-pm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Lee@...gul.tnic
Subject: Re: [PATCH][v8] PM / hibernate: Verify the consistent of e820 memory map by md5 value

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?

Thanks,
Rafael