From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36782) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XS9K5-0006Vw-Eh for qemu-devel@nongnu.org; Thu, 11 Sep 2014 14:42:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XS9Jv-00018v-JN for qemu-devel@nongnu.org; Thu, 11 Sep 2014 14:42:25 -0400 Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:40484) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XS9Jv-00018d-BM for qemu-devel@nongnu.org; Thu, 11 Sep 2014 14:42:15 -0400 Received: from /spool/local by e06smtp16.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 11 Sep 2014 19:42:13 +0100 Date: Thu, 11 Sep 2014 20:42:06 +0200 From: Greg Kurz Message-ID: <20140911204206.006fe667@bahia.local> In-Reply-To: <1410459530-29832-1-git-send-email-mst@redhat.com> References: <1410459530-29832-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5] virtio-pci: enable bus master for old guests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Jason Wang , Cedric Le Goater , qemu-devel@nongnu.org, Anthony Liguori , qemu-stable@nongnu.org On Thu, 11 Sep 2014 21:20:03 +0300 "Michael S. Tsirkin" wrote: > commit cc943c36faa192cd4b32af8fe5edb31894017d35 > pci: Use bus master address space for delivering MSI/MSI-X messages > breaks virtio-net for rhel6.[56] x86 guests because they don't > enable bus mastering for virtio PCI devices. For the same reason, > rhel6.[56] ppc64 guests cannot boot on a virtio-blk disk anymore. > > Old guests forgot to enable bus mastering, enable it automatically on > DRIVER (guests use some devices before DRIVER_OK). > > Reported-by: Greg Kurz > Signed-off-by: Michael S. Tsirkin > --- > Sorry, v4 was broken - forgot to commit before git format-patch. > Here's the correct version. > Still not tested - will do next week. > Testing reports appreciated meanwhile. > Nice patch indeed ! :) Reviewed-by: Greg Kurz Tested-by: Greg Kurz Cc'ing qemu-stable as Michael said he would queue the initial bus master patch for 2.1.2. > hw/virtio/virtio-pci.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index ddb5da1..a827cd4 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -314,6 +314,16 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) > msix_unuse_all_vectors(&proxy->pci_dev); > } > > + /* Linux before 2.6.34 drives the device without enabling > + the PCI device bus master bit. Enable it automatically > + for the guest. This is a PCI spec violation but so is > + initiating DMA with bus master bit clear. */ > + if (val == (VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER)) { > + pci_default_write_config(&proxy->pci_dev, PCI_COMMAND, > + proxy->pci_dev.config[PCI_COMMAND] | > + PCI_COMMAND_MASTER, 1); > + } > + > /* Linux before 2.6.34 sets the device as OK without enabling > the PCI device bus master bit. In this case we need to disable > some safety checks. */ -- Gregory Kurz kurzgreg@fr.ibm.com gkurz@linux.vnet.ibm.com Software Engineer @ IBM/Meiosys http://www.ibm.com Tel +33 (0)562 165 496 "Anarchy is about taking complete responsibility for yourself." Alan Moore.