linux-kernel - Re: [kvm-devel] [GIT PULL][RESEND] Late KVM Updates for the 2.6.23 merge window

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Message-ID: <alpine.LFD.0.999.0707201633390.27249@woody.linux-foundation.org>
Date:	Fri, 20 Jul 2007 16:37:48 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	S.Çağlar Onur <caglar@...dus.org.tr>
cc:	kvm-devel@...ts.sourceforge.net, Avi Kivity <avi@...ranet.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [kvm-devel] [GIT PULL][RESEND] Late KVM Updates for the 2.6.23
 merge window



On Sat, 21 Jul 2007, S.Çağlar Onur wrote:
> 
> With Linus's latest git, shutting down a guest (fired with -smp 2 -m 512) sometimes 
> ends up like [1], this occured as soon as qemu window closed.
> 
> [1] http://cekirdek.pardus.org.tr/~caglar/kvm/dmesg.latest

[  737.460654] Bad page state in process 'qemu-kvm'
[  737.460656] page:f5e68000 flags:0xea020000 mapping:00000000 mapcount:2 count:0
[  737.460657] Trying to fix it up, but a reboot is needed
[  737.460659] Backtrace:
[  737.460691]  [<c0159e70>] bad_page+0x64/0x8e
[  737.460733]  [<c015a7ee>] free_hot_cold_page+0x68/0x15a

That's the "free_pages_check()", and in particular it seems to be 
"page_mapcount()" being non-zero that triggered that thing.

So it looks like something in KVM isn't coherent about the mapping vs the 
usage counters..

		Linus
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