Re: [Qemu-devel] [PATCH] virtio-pci: Clear IRQ at reset

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

On Thu, Mar 12, 2015 at 02:40:55PM +0800, Fam Zheng wrote:
> Currently we could leave PCI IRQ asserted even after reset, it is safer
> to clear it.
> 
> In the case that a buggy driver has disabled MSI-X unintentially, we may
> have already injected IRQ in previous virtio_pci_notify, which will not
> be cleared by guest because it doesn't expect it (i.e. no irq handler).
> However the driver may eventually notice the unresponsiveness and reset
> the device, at that point, clearing the irq is meaningful.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>

I don't think we care about buggy drivers being able to recover, but the
same would apply to e.g. kdump when using virtio blk/scsi after a crash,
correct?

> ---
>  hw/virtio/virtio-pci.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index e7baf7b..2600f1e 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -988,6 +988,7 @@ static void virtio_pci_reset(DeviceState *qdev)
>      virtio_pci_stop_ioeventfd(proxy);
>      virtio_bus_reset(bus);
>      msix_unuse_all_vectors(&proxy->pci_dev);
> +    pci_irq_deassert(&proxy->pci_dev);
>  }
>  
>  static Property virtio_pci_properties[] = {
> -- 
> 1.9.3