Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 09, 2014 at 09:13:38AM -0500, Michael Roth wrote:
> Quoting Michael S. Tsirkin (2014-09-08 11:05:02)
> > 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.
> 
> I've already backed out the other patch, and it looks we'll have to stick
> with that for now with the release being tomorrow.

That's fine.

> Will queue these back
> up for 2.1.2 though.
> > 
> > Cc: qemu-stable@nongnu.org
> > Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  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:
> > -- 
> > MST