From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753072AbbHMOxe (ORCPT ); Thu, 13 Aug 2015 10:53:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48091 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751692AbbHMOxc (ORCPT ); Thu, 13 Aug 2015 10:53:32 -0400 Subject: Re: [PATCH 2/2] KVM: x86: fix edge EOI and IOAPIC reconfig race To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org References: <1439473570-13763-1-git-send-email-rkrcmar@redhat.com> <1439473570-13763-3-git-send-email-rkrcmar@redhat.com> Cc: kvm@vger.kernel.org, Steve Rutherford , stable@vger.kernel.org From: Paolo Bonzini Message-ID: <55CCAF5D.8050204@redhat.com> Date: Thu, 13 Aug 2015 16:53:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1439473570-13763-3-git-send-email-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/08/2015 15:46, Radim Krčmář wrote: > 1) IOAPIC inject a vector from i8254 > 2) guest reconfigures that vector's VCPU and therefore eoi_exit_bitmap > on original VCPU gets cleared > 3) guest's handler for the vector does EOI > 4) KVM's EOI handler doesn't pass that vector to IOAPIC because it is > not in that VCPU's eoi_exit_bitmap > 5) i8254 stops working > > This creates an unwanted situation if the vector is reused by a > non-IOAPIC source, but I think it is so rare that we don't want to make > the solution more sophisticated. What happens if the vector is changed in step 2? __kvm_ioapic_update_eoi won't match the redirection table entry. How do you reproduce the bug? Paolo