From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42093) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XT7F5-0004yz-9e for qemu-devel@nongnu.org; Sun, 14 Sep 2014 06:41:21 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XT7Ez-0005WI-58 for qemu-devel@nongnu.org; Sun, 14 Sep 2014 06:41:15 -0400 Date: Sun, 14 Sep 2014 13:44:20 +0300 From: "Michael S. Tsirkin" Message-ID: <20140914104420.GA27188@redhat.com> References: <1410459530-29832-1-git-send-email-mst@redhat.com> <20140911204206.006fe667@bahia.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140911204206.006fe667@bahia.local> 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: Greg Kurz Cc: Jason Wang , Cedric Le Goater , qemu-devel@nongnu.org, Anthony Liguori , qemu-stable@nongnu.org On Thu, Sep 11, 2014 at 08:42:06PM +0200, Greg Kurz wrote: > 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. In my opinion it's best to keep the initial patch off stable. > > 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.