From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753035AbaIXL4A (ORCPT ); Wed, 24 Sep 2014 07:56:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62775 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbaIXLz6 (ORCPT ); Wed, 24 Sep 2014 07:55:58 -0400 Date: Wed, 24 Sep 2014 14:59:13 +0300 From: "Michael S. Tsirkin" To: Ben Hutchings Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Amit Shah , Rusty Russell , virtualization@lists.linux-foundation.org Subject: Re: [PATCH RFC] virtio_pci: fix virtio spec compliance on restore Message-ID: <20140924115913.GA32179@redhat.com> References: <1411468217-18130-1-git-send-email-mst@redhat.com> <1411522047.3659.10.camel@decadent.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1411522047.3659.10.camel@decadent.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 24, 2014 at 02:27:27AM +0100, Ben Hutchings wrote: > On Tue, 2014-09-23 at 13:32 +0300, Michael S. Tsirkin wrote: > > On restore, virtio pci does the following: > > + set features > > + init vqs etc - device can be used at this point! > > + set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits > > > > This is in violation of the virtio spec, which > > requires the following order: > > - ACKNOWLEDGE > > - DRIVER > > - init vqs > > - DRIVER_OK > > > > Cc: stable@vger.kernel.org > > Cc: Amit Shah > > Signed-off-by: Michael S. Tsirkin > [...] > > What concrete problem does this fix, such that it should be applied to > stable branches? > > Ben. It will break with hypervisors that assume spec compliant behaviour. I would like this applied to stable branches so hypervisors don't need to support broken behaviour forever. -- MST