From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roedel, Joerg" Subject: Re: [PATCH 16/22] KVM: MMU: Track page fault data in struct vcpu Date: Tue, 4 May 2010 14:00:39 +0200 Message-ID: <20100504120039.GH28950@amd.com> References: <1272364712-17425-1-git-send-email-joerg.roedel@amd.com> <1272364712-17425-17-git-send-email-joerg.roedel@amd.com> <4BD6DF7C.1090203@redhat.com> <20100503163221.GB28950@amd.com> <4BDFD295.7000702@redhat.com> <20100504091157.GC28950@amd.com> <4BDFE6C2.2040601@redhat.com> <20100504093709.GE28950@amd.com> <4BDFECD1.8040109@redhat.com> <4BDFEDFA.3090209@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Marcelo Tosatti , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <4BDFEDFA.3090209@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, May 04, 2010 at 05:50:50AM -0400, Avi Kivity wrote: > On 05/04/2010 12:45 PM, Avi Kivity wrote: > > > > > > Just a silly bug. kvm_pdptr_read() can cause a guest memory read on > > svm, in this case with the mmu lock taken. I'll post something to fix > > it. > > I guess this was not reported because most svm machines have npt, and > this requires npt=0 to trigger. Nonpae paging disables npt, so you were > hit. Interestingly, nsvm makes it more likely to appear, since npt on > i386+pae will need the pdptrs. Hmm, actually it happened on 32 bit with npt enabled. I think this can trigger when mmu_alloc_roots is called for an pae guest because it accidentially tries read the root_gfn from the guest before it figures out that it runs with tdp and omits the gfn read from the guest. I need to touch this for nested-npt and will look into a way improving this. Joerg