From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: Debugging an inconsistent shadow page table
Date: Sun, 26 Apr 2009 14:39:52 +0300
Message-ID: <20090426113952.GU24095@redhat.com>
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Cc: Avi Kivity <avi@redhat.com>, kvm-devel <kvm@vger.kernel.org>
To: Jan Kiszka <jan.kiszka@web.de>
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On Sun, Apr 26, 2009 at 01:36:22PM +0200, Jan Kiszka wrote:
> Gleb Natapov wrote:
> > On Sun, Apr 26, 2009 at 01:11:40PM +0200, Jan Kiszka wrote:
> >> That raise a question for a kvm-mmu newbie like me:
> >>
> >> If a page of the qemu process gets pushed around (here likely due to
> >> fork()->exec(smbd)->COW), how will kvm's shadow table catch up? Via
> >> MMU_NOTIFIER?
> >>
> >> I'm on a 2.6.25 kernel, and that means without CONFIG_MMU_NOTIFIER. So
> >> far I assumed that kernels without this feature do not work optimally,
> >> but they won't break my guests...
> >>
> > Guest memory is not COWed on fork (madvise(MADV_DONTFORK))
> 
> Yeah... but that's missing upstream! Will cross-check and then post a
> fix for qemu.
> 
> Out of curiosity: What's the mechanism to update the shadow table after
> swap-out/swap-in?
> 
I don't think guest memory is swappable without mmu notifiers. 

--
			Gleb.