Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754551Ab0DWDi7 (ORCPT ); Thu, 22 Apr 2010 23:38:59 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:52466 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754117Ab0DWDi5 (ORCPT ); Thu, 22 Apr 2010 23:38:57 -0400 Message-ID: <4BD11596.90900@cn.fujitsu.com> Date: Fri, 23 Apr 2010 11:35:50 +0800 From: Xiao Guangrong User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , KVM list , LKML Subject: Re: [PATCH 6/10] KVM MMU: don't write-protect if have new mapping to unsync page References: <4BCFE581.8050305@cn.fujitsu.com> <4BCFE8F0.7010509@cn.fujitsu.com> <20100422192947.GA2280@amt.cnet> In-Reply-To: <20100422192947.GA2280@amt.cnet> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1910 Lines: 54 Marcelo Tosatti wrote: >> role = vcpu->arch.mmu.base_role; >> @@ -1332,12 +1336,16 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, >> hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link) >> if (sp->gfn == gfn) { >> if (sp->unsync) >> - if (kvm_sync_page(vcpu, sp)) >> - continue; >> + unsync_sp = sp; > Hi Marcelo, Thanks for your comments, maybe the changlog is not clear, please allow me explain here. 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) > > I don't see a reason why you can't create a new mapping to an unsync > page. The code already creates shadow pte entries using unsync > pagetables. Do you means the case 2? In the original code, it unsync-ed gfn's unsync page first regardless it's whether broke unsync rule: | hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link) | if (sp->gfn == gfn) { | if (sp->unsync) | if (kvm_sync_page(vcpu, sp)) And, my English is poor, sorry if i misunderstand your comment :-( Xiao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/