linux-kernel - Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap

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Message-ID: <20100413145927.GA24128@amt.cnet>
Date:	Tue, 13 Apr 2010 11:59:27 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, KVM list <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] KVM MMU: fix kvm_mmu_zap_page() and its calling path

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.


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