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

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2014-09-08 18:05, 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 <gkurz@linux.vnet.ibm.com>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

I didn't signed off as I didn't write this patch ;). But you can add my
reviewed-by if you like.

Jan

> 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:
> 

-- 
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