Re: [PATCH v1 2/8] virtio-pci: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA

[Michael S. Tsirkin]

On Mon, Mar 04, 2024 at 02:46:06PM -0500, Jonah Palmer wrote:
> Prevent ioeventfd from being enabled/disabled when a virtio-pci
> device has negotiated the VIRTIO_F_NOTIFICATION_DATA transport
> feature.
> 
> Due to ioeventfd not being able to carry the extra data associated with
> this feature, the ioeventfd should be left in a disabled state for
> emulated virtio-pci devices using this feature.
> 
> Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>

I thought hard about this. I propose that for now,
instead of disabling ioevetfd silently we error out unless
user disabled it for us.
WDYT?


> ---
>  hw/virtio/virtio-pci.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index d12edc567f..287b8f7720 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -417,13 +417,15 @@ static void virtio_ioport_write(void *opaque, uint32_t 
> addr, uint32_t val)
>          }
>          break;
>      case VIRTIO_PCI_STATUS:
> -        if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> +        if (!(val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +            !virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
>              virtio_pci_stop_ioeventfd(proxy);
>          }
>  
>          virtio_set_status(vdev, val & 0xFF);
>  
> -        if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
> +        if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> +            !virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
>              virtio_pci_start_ioeventfd(proxy);
>          }
>  
> -- 
> 2.39.3