On Wed, Sep 10, 2014 at 01:44:49PM +0530, Nikunj A Dadhania wrote:
> Greg Kurz <gk...@linux.vnet.ibm.com> writes:
>
> > On Mon, 8 Sep 2014 19:05:02 +0300
> > "Michael S. Tsirkin" <m...@redhat.com> 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-sta...@nongnu.org
> >> Reported-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> >> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> >> Signed-off-by: Michael S. Tsirkin <m...@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:
> >
> > 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 kurzg...@fr.ibm.com
> > gk...@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.
