From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39328) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRU0t-00080m-Js for qemu-devel@nongnu.org; Tue, 09 Sep 2014 18:35:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XRU0l-00050N-F9 for qemu-devel@nongnu.org; Tue, 09 Sep 2014 18:35:51 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:36123) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRU0l-0004zH-3R for qemu-devel@nongnu.org; Tue, 09 Sep 2014 18:35:43 -0400 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 9 Sep 2014 23:35:40 +0100 Date: Wed, 10 Sep 2014 00:35:32 +0200 From: Greg Kurz Message-ID: <20140910003532.22d72602@bahia.local> In-Reply-To: <1410192283-4026-1-git-send-email-mst@redhat.com> References: <1410192283-4026-1-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] 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: Alexey Kardashevskiy , Jan Kiszka , qemu-devel@nongnu.org, Anthony Liguori , qemu-stable@nongnu.org On Mon, 8 Sep 2014 19:05:02 +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 > > Old guests forgot to enable bus mastering, enable it > automatically on DRIVER_OK. > > Note: we should either back out the original patch from > stable or apply this one on top. > > Cc: qemu-stable@nongnu.org > Reported-by: Greg Kurz > Signed-off-by: Jan Kiszka > Signed-off-by: Michael S. Tsirkin > --- > hw/virtio/virtio-pci.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index ddb5da1..af937d2 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -320,6 +320,8 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) > if ((val & VIRTIO_CONFIG_S_DRIVER_OK) && > !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, > + true); > } > break; > case VIRTIO_MSI_CONFIG_VECTOR: Cc'ing Alexey for some SLOF and early boot of the ppc64 kernel expertise. Michael, This was enough to fix virtio-net in the rhel6.5 x86 guest case. Unfortunately, this fails for rhel6.5 ppc64 because it is never called... I did some debugging: it looks like the guest kernel calls the OF quisece call to flush pending DMA and disables bus master on the virtio-blk device (PCI_COMMAND == 0x3). The guest then continues to boot and hangs... It appears that waiting for the guest to issue VIRTIO_CONFIG_S_DRIVER_OK is not enough. Since we need this for MSI to work, I tried the following and it fixes the issue: diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index af937d2..3d72aa8 100644 --- a/hw/virtio/virtio-pci.c +++ b/hw/virtio/virtio-pci.c @@ -111,9 +111,14 @@ static void virtio_pci_notify(DeviceState *d, uint16_t vector) { VirtIOPCIProxy *proxy = to_virtio_pci_proxy_fast(d); - if (msix_enabled(&proxy->pci_dev)) + if (msix_enabled(&proxy->pci_dev)) { + if (!(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { + proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region, + true); + } msix_notify(&proxy->pci_dev, vector); - else { + } else { VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus); pci_set_irq(&proxy->pci_dev, vdev->isr & 1); } If this is acceptable, I'll make it a helper and squash it into your patch. Thoughts ? -- 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.