From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v8 00/11] KVM: MMU: fast zap all shadow pages Date: Sun, 09 Jun 2013 17:06:24 +0800 Message-ID: <51B44590.7030009@linux.vnet.ibm.com> References: <1369960590-14138-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130609085342.GI4725@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Gleb Natapov Return-path: In-Reply-To: <20130609085342.GI4725@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 06/09/2013 04:53 PM, Gleb Natapov wrote: > On Fri, May 31, 2013 at 08:36:19AM +0800, Xiao Guangrong wrote: >> Hi Gleb, Paolo, Marcelo, >> >> I have putted the potential controversial patches to the latter that are >> patch 8 ~ 10, patch 11 depends on patch 9. Other patches are fully reviewed, >> I think its are ready for being merged. If not luck enough, further discussion >> is needed, could you please apply that patches first? :) >> >> Thank you in advance! >> >> Some points are raised during discussion but missed in this version: >> 1) Gleb's idea that skip obsolete pages in the hast list walker >> >> Unfortunately, it is not safe. There has a window between updating >> valid-gen and reloading mmu, in that window, the obsolete page can >> be used by vcpu, but the guest page table fail to be write-protected >> (since the obsolete page is skipped in mmu_need_write_protect()). >> > Can you elaborate on how this can happen. valid_gen is updated under > mmu_lock and reloading of mmus happens under the same lock, so for all > other vcpus this should look like atomic thing. You're right. Actually, i made another optimization patch in this version that moves kvm_reload_remote_mmus() out of mmu-lock, but did not attach it into this series. It seems my brain is not parallel-able enough. :(