linux-kernel - Re: kvm splat in mmu_spte_clear_track

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Message-ID: <20170827123505.u4kb24kigjqwa2t2@angband.pl>
Date:   Sun, 27 Aug 2017 14:35:05 +0200
From:   Adam Borowski <kilobyte@...band.pl>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Wanpeng Li <kernellwp@...il.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: kvm splat in mmu_spte_clear_track_bits

On Fri, Aug 25, 2017 at 03:40:50PM +0200, Paolo Bonzini wrote:
> On 25/08/2017 15:14, Adam Borowski wrote:
> >>> I would also try commit 1372324b328cd5dabaef5e345e37ad48c63df2a9 to
> >>> identify whether it was caused by a KVM change in 4.13 or something
> >>> else.
> > I've ran different guests for a couple of hours, no explosions.  Thus it
> > looks like updating Cornelia's email address isn't the cause.
> > 
> > Too bad, there's 15k commits between 1372324b and 7f680d7ec315.
> 
> So:
> 
> - 4.12 works
> 
> - 1372324b328cd5dabaef5e345e37ad48c63df2a9 works
> 
> - 4.13-rc6 fails
> 
> The next ones to test are going to be
> c136b84393d4e340e1b53fc7f737dd5827b19ee5 and 4.13-rc1.

c136b84393d4e340e1b53fc7f737dd5827b19ee5 works

4.13-rc1 works
Which actually isn't so surprising, as I pull from linus/master every Sunday
night/Monday morning, so I'd would have noticed KVM breakage sooner.

4.13-rc4 works

4.13-rc5 works (but ↓)

v4.13-rc5-173-g58d4e450a490 works... uh oh.
It shouldn't -- it's merge-base between mainline and what I was running on
the initial crash, and I'm sure anything non-mainline I had isn't the
culprit.  After a couple of hours of running various loads inside and
outside KVM, I finally got it to crash.

4.13-rc5 retested fails
Crashed only after two hours or so of testing.

4.13-rc4 apparently works
It survived several hours of varied tests (like 5 debian-installer runs, a
win10 point release upgrade, some hurd package building, openbsd, etc),
all while the host was likewise busy.

Thus: to the best of my knowledge, the problem is between 4.13-rc4 and 4.13-rc5
but I wouldn't bet my life on it.

Meow!
-- 
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⢿⡄⠘⠷⠚⠋⠀                                 -- Genghis Ht'rok'din
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