From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: nVMX: fix shadow on EPT Date: Wed, 09 Oct 2013 18:19:52 +0200 Message-ID: <52558228.9010602@redhat.com> References: <20131009161319.GO3574@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Kashyap Chamarthy To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:18737 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755046Ab3JIQT6 (ORCPT ); Wed, 9 Oct 2013 12:19:58 -0400 In-Reply-To: <20131009161319.GO3574@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Il 09/10/2013 18:13, Gleb Natapov ha scritto: > 72f857950f6f19 broke shadow on EPT. This patch reverts it and fixes PAE > on nEPT (which reverted commit fixed) in other way. > > Shadow on EPT is now broken because while L1 builds shadow page table > for L2 (which is PAE while L2 is in real mode) it never loads L2's > GUEST_PDPTR[0-3]. They do not need to be loaded because without nested > virtualization HW does this during guest entry if EPT is disabled, > but in our case L0 emulates L2's vmentry while EPT is enables, so we > cannot rely on vmcs12->guest_pdptr[0-3] to contain up-to-date values > and need to re-read PDPTEs from L2 memory. This is what kvm_set_cr3() > is doing, but by clearing cache bits during L2 vmentry we drop values > that kvm_set_cr3() read from memory. > > So why the same code does not work for PAE on nEPT? kvm_set_cr3() > reads pdptes into vcpu->arch.walk_mmu->pdptrs[]. walk_mmu points to > vcpu->arch.nested_mmu while nested guest is running, but ept_load_pdptrs() > uses vcpu->arch.mmu which contain incorrect values. Fix that by using > walk_mmu in ept_(load|save)_pdptrs. > > Signed-off-by: Gleb Natapov The new fix also looks much more obvious. Applied to queue, thanks. Paolo