From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37538) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRdHE-00018A-Al for qemu-devel@nongnu.org; Wed, 10 Sep 2014 04:29:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XRdH9-0001dD-4N for qemu-devel@nongnu.org; Wed, 10 Sep 2014 04:29:20 -0400 Date: Wed, 10 Sep 2014 12:32:30 +0300 From: "Michael S. Tsirkin" Message-ID: <20140910093230.GB7902@redhat.com> References: <1410192283-4026-1-git-send-email-mst@redhat.com> <20140910003532.22d72602@bahia.local> <87oaunops6.fsf@abhimanyu.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87oaunops6.fsf@abhimanyu.in.ibm.com> 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: Nikunj A Dadhania Cc: Alexey Kardashevskiy , Jan Kiszka , qemu-stable@nongnu.org, qemu-devel@nongnu.org, Anthony Liguori On Wed, Sep 10, 2014 at 01:44:49PM +0530, Nikunj A Dadhania wrote: > Greg Kurz writes: > > > 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). > > Getting confused, above you are talking about virtio-net and here it is > virtio-blk. > > Anyways, the routines still remains same for both of them. From SLOF > during init we set DRIVER_OK, and after using the device during the > quiesce, called from linux kernel VIRTIO_CONFIG_S_FAILED is set and then > a VIRTIO_DEVICE_RESET is done. BTW, you really should start enabling bus mastering, avoid relying on the work-around we have for broken guests. > > 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.