Re: [PATCH 4/4] virtio_ring: preserve VIRTIO_F_RING_RESET in transport features

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

On Tue, Apr 07, 2026 at 08:39:04AM -0400, Andrew Stellman wrote:
> vring_transport_features() whitelists known transport feature bits and
> clears the rest via __virtio_clear_bit(). VIRTIO_F_RING_RESET is
> missing from the whitelist, so it is unconditionally cleared during
> feature negotiation. Drivers that depend on ring reset capability
> silently lose the feature.

Hmm was this observed in practice or just from code analysis?
And on which transport?
Because


static void vp_transport_features(struct virtio_device *vdev, u64 features)
{               
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        struct pci_dev *pci_dev = vp_dev->pci_dev;
                        
        if ((features & BIT_ULL(VIRTIO_F_SR_IOV)) &&
                        pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_SRIOV))
                __virtio_set_bit(vdev, VIRTIO_F_SR_IOV);
        
        if (features & BIT_ULL(VIRTIO_F_RING_RESET))
                __virtio_set_bit(vdev, VIRTIO_F_RING_RESET);
        

...



}




> Add VIRTIO_F_RING_RESET to the switch statement, matching the other
> transport-level features.
> 
> Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
> ---
>  drivers/virtio/virtio_ring.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index fbca7ce..2cb643f 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -3524,6 +3524,8 @@ void vring_transport_features(struct virtio_device *vdev)
>  			break;
>  		case VIRTIO_F_IN_ORDER:
>  			break;
> +		case VIRTIO_F_RING_RESET:
> +			break;
>  		default:
>  			/* We don't understand this bit. */
>  			__virtio_clear_bit(vdev, i);
> -- 
> 2.34.1