From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2 6/10] KVM MMU: don't write-protect if have new mapping to unsync page Date: Sun, 25 Apr 2010 13:00:00 +0300 Message-ID: <4BD412A0.1000101@redhat.com> References: <4BD3E306.4020202@cn.fujitsu.com> <4BD3E8AB.4020704@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , KVM list , LKML To: Xiao Guangrong Return-path: In-Reply-To: <4BD3E8AB.4020704@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/25/2010 10:00 AM, Xiao Guangrong wrote: > Two cases maybe happen in kvm_mmu_get_page() function: > > - one case is, the goal sp is already in cache, if the sp is unsync, > we only need update it to assure this mapping is valid, but not > mark it sync and not write-protect sp->gfn since it not broke unsync > rule(one shadow page for a gfn) > > - another case is, the goal sp not existed, we need create a new sp > for gfn, i.e, gfn (may)has another shadow page, to keep unsync rule, > we should sync(mark sync and write-protect) gfn's unsync shadow page. > After enabling multiple unsync shadows, we sync those shadow pages > only when the new sp not allow to become unsync(also for the unsyc > rule, the new rule is: allow all pte page become unsync) > Another interesting case is to create new shadow pages in the unsync state. That can help when the guest starts a short lived process: we can avoid write protecting its pagetables completely. Even if we do sync them, we can sync them in a batch instead of one by one, saving IPIs. -- error compiling committee.c: too many arguments to function