From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753662AbcBHQ3e (ORCPT ); Mon, 8 Feb 2016 11:29:34 -0500 Received: from prv-mh.provo.novell.com ([137.65.248.74]:54124 "EHLO prv-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751870AbcBHQ3c convert rfc822-to-8bit (ORCPT ); Mon, 8 Feb 2016 11:29:32 -0500 Message-Id: <56B85FFA02000048001251CE@prv-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.2.0 Date: Mon, 08 Feb 2016 09:29:30 -0700 From: "Bruce Rogers" To: "Paolo Bonzini" , , Cc: , Subject: Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset References: <1454539876-8310-1-git-send-email-brogers@suse.com> <56B8AFAF.7090509@redhat.com> In-Reply-To: <56B8AFAF.7090509@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 2/8/2016 at 08:09 AM, Paolo Bonzini wrote: > > On 03/02/2016 23:51, Bruce Rogers wrote: >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index e2951b6..21507b4 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -4993,8 +4993,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool > init_event) >> vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid); >> >> cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET; >> - vmx_set_cr0(vcpu, cr0); /* enter rmode */ >> vmx->vcpu.arch.cr0 = cr0; >> + vmx_set_cr0(vcpu, cr0); /* enter rmode */ > > Your comment that the assignment is redundant is correct, but I am > afraid that this fix is also wrong. In particular, it would not cause > exit_lmode and enter_rmode to be called. > > You are not describing which call to kvm_mmu_reset_context was messed > up, so I'm not sure how your patch is fixing things. This is in the context of AP sending INIT to BSP with unrestricted_guest=N. So the call sequence where I see the issue is: kvm_apic_accept_events() -> kvm_vcpu_reset() -> vmx_vcpu_reset() -> vmx_set_cr0() -> enter_rmode() -> kvm_mmu_reset_context(). enter_rmode is called in the case I am testing. Bruce