linux-kernel - Re: [PATCH 09/12] KVM: MMU: introduce pte-list lockless walker

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Message-ID: <20130828094630.GR22899@redhat.com>
Date:	Wed, 28 Aug 2013 12:46:30 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	avi.kivity@...il.com, mtosatti@...hat.com, pbonzini@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 09/12] KVM: MMU: introduce pte-list lockless walker

On Wed, Aug 28, 2013 at 05:33:49PM +0800, Xiao Guangrong wrote:
> > Or what if desc is moved to another rmap, but then it
> > is moved back to initial rmap (but another place in the desc list) so
> > the check here will not catch that we need to restart walking?
> 
> It is okay. We always add the new desc to the head, then we will walk
> all the entires under this case.
> 
Which races another question: What if desc is added in front of the list
behind the point where lockless walker currently is?

> Right?
Not sure. While lockless walker works on a desc rmap can be completely
destroyed and recreated again. It can be any order.

--
			Gleb.
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