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

[Michael Roth <mdroth@linux.vnet.ibm.com>]

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. 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