From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v2 5/5] KVM: MMU: retry #PF for softmmu Date: Mon, 15 Nov 2010 17:55:25 +0800 Message-ID: <4CE1038D.9020403@cn.fujitsu.com> References: <4CDCE2B0.7000601@cn.fujitsu.com> <4CDCE3C2.9030107@cn.fujitsu.com> <4CDFBE00.2000802@redhat.com> <4CE0C45C.809@cn.fujitsu.com> <4CE0FDBC.20505@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Gleb Natapov , LKML , KVM To: Avi Kivity Return-path: In-Reply-To: <4CE0FDBC.20505@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 11/15/2010 05:30 PM, Avi Kivity wrote: >> Yeah, this 'retry' is unnecessary if the process is killed, but this >> case is infrequent, the most case is the process keeps running and try >> to access the fault address later. > > The problem is that if we retry in this case, we install an incorrect spte? > ...... >> can avoid if the page mapping have been fixed. > > The guest may have changed page directories or other levels. > ...... >> > Or another thread may have mmap()ed something else over the >> > same address. >> >> The mmap virtual address is also visible for other threads since the >> threads >> have the same page table, so i think this case is the same as above? > > Again, don't we install the wrong spte in this case? > I think it doesn't corrupts spte since we will walk guest page table again and map it to shadow pages when we retry #PF.