From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40734) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgYIS-0006OO-5Z for qemu-devel@nongnu.org; Tue, 21 Oct 2014 08:12:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgYIK-0002Vo-MC for qemu-devel@nongnu.org; Tue, 21 Oct 2014 08:12:16 -0400 Message-ID: <54464D97.5080006@suse.de> Date: Tue, 21 Oct 2014 14:12:07 +0200 From: Alexander Graf MIME-Version: 1.0 References: <1413788223-16235-1-git-send-email-mst@redhat.com> <54453398.2060102@suse.de> <20141021101650.GA22793@redhat.com> <5446450B.8000600@suse.de> <20141021121022.GA23466@redhat.com> In-Reply-To: <20141021121022.GA23466@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3] virtio-pci: fix migration for pci bus master List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, Anthony Liguori On 21.10.14 14:10, Michael S. Tsirkin wrote: > On Tue, Oct 21, 2014 at 01:35:39PM +0200, Alexander Graf wrote: >> >> >> On 21.10.14 12:16, Michael S. Tsirkin wrote: >>> On Mon, Oct 20, 2014 at 06:08:56PM +0200, Alexander Graf wrote: >>>> >>>> >>>> On 20.10.14 08:58, Michael S. Tsirkin wrote: >>>>> Current support for bus master (clearing OK bit) together with the need to >>>>> support guests which do not enable PCI bus mastering, leads to extra state in >>>>> VIRTIO_PCI_FLAG_BUS_MASTER_BUG bit, which isn't robust in case of cross-version >>>>> migration for the case when guests use the device before setting DRIVER_OK. >>>>> >>>>> Rip out this code, and replace it: >>>>> - Modern QEMU doesn't need VIRTIO_PCI_FLAG_BUS_MASTER_BUG >>>>> so just drop it for latest machine type. >>>>> - For compat machine types, set PCI_COMMAND if DRIVER_OK >>>>> is set. >>>>> >>>>> As this is needed for 2.1 for both pc and ppc, move PC_COMPAT macros from pc.h >>>>> to a new common header. >>>>> >>>>> Reviewed-by: Greg Kurz >>>>> Tested-by: Greg Kurz >>>>> Signed-off-by: Michael S. Tsirkin >>>>> --- >>>>> >>>>> Alexander, could you pls ack me merging this? >>>>> Thanks! >>>> >>>> Have you tried whether this works with old kernel versions? We >>>> introduced the broken flag for very specific old kernel versions that >>>> got their flags wrong IIRC. >>>> >>>> >>>> Alex >>> >>> Yes. The point is that since 2.1 the broken flag isn't effective >>> anymore: when bus master is off, PCI blocks outgoing transactions and >>> setting internal flags isn't going to help. >>> >>> Instead, we detect a buggy guest and immediately enable bus master for >>> it - no need for a separate flag. >> >> Ok, works for me then. >> >> >> Alex > > cool. > Gerd tells me there's a conflict with your next tree: > would you like for me to wait until it's merged, > or go ahead and send pull request and rebase yours on top? Whoever sends it first wins I'd say ;) Alex