linux-kernel - Re: 4.13-rc7: WARNING at arch/x86/kvm/mmu.c:717 (and a crash thereafter)

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Date:   Mon, 28 Aug 2017 16:41:15 +0200
From:   Mike Galbraith <efault@....de>
To:     Takashi Iwai <tiwai@...e.de>, Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: 4.13-rc7: WARNING at arch/x86/kvm/mmu.c:717 (and a crash
 thereafter)

On Mon, 2017-08-28 at 15:52 +0200, Mike Galbraith wrote:
> On Mon, 2017-08-28 at 14:26 +0200, Takashi Iwai wrote:
> > Hi,
> > 
> > I seem to get a kernel warning when running KVM on Dell desktop with
> > IvyBridge like below.  As you can see, a bad page BUG is triggered
> > after that, too.  The problem is not triggered always, but it happens
> > occasionally.
> > 
> > I haven't seen this on 4.13-rc4 at all, and IIRC, it started happening
> > since rc5.  So this might be a regression at rc5.  But, as it doesn't
> > happen always, I can't be 100% sure about it, and it's quite difficult
> > to bisect (the test case isn't reliable), unfortunately.
> > 
> > Any hint for further debugging this?
> 
> Maybe a way to make failure more likely.  This is an RT kernel, but
> trying to build a fat kernel over NFS from a KVM clone of my
> workstation (full topology, half of ram) didn't survive one build.

Bah, plain master in guest/host survived.

	-Mike