From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752380AbaHYJQk (ORCPT ); Mon, 25 Aug 2014 05:16:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33266 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000AbaHYJQj (ORCPT ); Mon, 25 Aug 2014 05:16:39 -0400 Message-ID: <53FAFEE0.9000408@redhat.com> Date: Mon, 25 Aug 2014 11:16:16 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Wanpeng Li CC: Marcelo Tosatti , Gleb Natapov , Zhang Yang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: fix xen guest panic due to lack of KVM_REQ_EVENT References: <1408953506-7289-1-git-send-email-wanpeng.li@linux.intel.com> <53FAFB53.7040806@redhat.com> <20140825090822.GA4955@kernel> In-Reply-To: <20140825090822.GA4955@kernel> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 25/08/2014 11:08, Wanpeng Li ha scritto: > Hi Paolo, > On Mon, Aug 25, 2014 at 11:01:07AM +0200, Paolo Bonzini wrote: >> Il 25/08/2014 09:58, Wanpeng Li ha scritto: >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>> index c10408e..b7c0073 100644 >>> --- a/arch/x86/kvm/x86.c >>> +++ b/arch/x86/kvm/x86.c >>> @@ -4928,6 +4928,8 @@ static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask) >>> if (!mask) >>> kvm_make_request(KVM_REQ_EVENT, vcpu); >>> } >>> + if (!(int_shadow || mask)) >>> + kvm_make_request(KVM_REQ_EVENT, vcpu); >>> } >>> >>> static void inject_emulated_exception(struct kvm_vcpu *vcpu) >> >> No, this patch undoes the optimization in the buggy patch. >> >> A KVM_REQ_EVENT must be missing somewhere else. >> > > Could you give some tips in order that I can figure it out? I have no idea right now (I was planning to debug it this week). (BTW, look at the original commit that introduced KVM_REQ_EVENT -- https://git.kernel.org/cgit/virt/kvm/kvm.git/commit/?id=3842d135 -- and compare the patch and the commit message. You can see that it was added to the emulator because it is a "place that can set EFLAGS" and this idea is preserved in the buggy patch). The important thing is that (despite Xen being involved) this is not related to nested virtualization. So I would first of all try to see if some module parameter makes it go away (apicv and unrestricted mode especially), then capture a trace of the panic. At least this is how I was planning to start... :) Paolo