From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path
Date: Wed, 14 Apr 2010 13:31:20 -0300
Message-ID: <20100414163120.GA5489@amt.cnet>
References: <4BC2D2E2.1030604@cn.fujitsu.com>
 <4BC2D345.100@cn.fujitsu.com>
 <20100412171037.GB4976@amt.cnet>
 <4BC3CA16.6020106@cn.fujitsu.com>
 <20100413145927.GA24128@amt.cnet>
 <4BC52505.6000502@cn.fujitsu.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Avi Kivity <avi@redhat.com>, KVM list <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <4BC52505.6000502@cn.fujitsu.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Wed, Apr 14, 2010 at 10:14:29AM +0800, Xiao Guangrong wrote:
> 
> 
> Marcelo Tosatti wrote:
> > On Tue, Apr 13, 2010 at 09:34:14AM +0800, Xiao Guangrong wrote:
> >>
> >> Marcelo Tosatti wrote:
> >>
> >>>> @@ -1483,8 +1483,8 @@ static int mmu_zap_unsync_children(struct kvm *kvm,
> >>>>  		for_each_sp(pages, sp, parents, i) {
> >>>>  			kvm_mmu_zap_page(kvm, sp);
> >>>>  			mmu_pages_clear_parents(&parents);
> >>>> +			zapped++;
> >>>>  		}
> >>>> -		zapped += pages.nr;
> >>>>  		kvm_mmu_pages_init(parent, &parents, &pages);
> >>>>  	}
> >>> Don't see why this is needed? The for_each_sp loop uses pvec.nr.
> >> I think mmu_zap_unsync_children() should return the number of zapped pages then we
> >> can adjust the number of free pages in kvm_mmu_change_mmu_pages(), but pages.nr no
> >> only includes the unsync/zapped pages but also includes their parents.
> > 
> > Oh i see. I think its safer to check for list_empty then to rely on
> > proper accounting there, like __kvm_mmu_free_some_pages does.
> 
> Do you mean that we'd better add WARN_ON(list_empty()) code in kvm_mmu_zap_page()?

Just break out of the loop if
list_empty(&vcpu->kvm->arch.active_mmu_pages).