Re: [PATCH v2] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

Viktor Prutyanov
2023-03-21T09:02:54Z

On Tue, Mar 21, 2023 at 5:29 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Tue, Mar 21, 2023 at 7:21 AM Viktor Prutyanov <viktor@daynix.com> wrote:
> >
> > According to VirtIO spec v1.2, VIRTIO_F_NOTIFICATION_DATA feature
> > indicates that the driver passes extra data along with the queue
> > notifications.
> >
> > In a split queue case, the extra data is 16-bit available index. In a
> > packed queue case, the extra data is 1-bit wrap counter and 15-bit
> > available index.
> >
> > Add support for this feature for MMIO and PCI transports. Channel I/O
> > transport will not accept this feature.
> >
> > Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
> > ---
> >
> > v2: reject the feature in virtio_ccw, replace __le32 with u32
> >
> > drivers/s390/virtio/virtio_ccw.c | 4 +---
> > drivers/virtio/virtio_mmio.c | 15 ++++++++++++++-
> > drivers/virtio/virtio_pci_common.c | 10 ++++++++++
> > drivers/virtio/virtio_pci_common.h | 4 ++++
> > drivers/virtio/virtio_pci_legacy.c | 2 +-
> > drivers/virtio/virtio_pci_modern.c | 2 +-
> > drivers/virtio/virtio_ring.c | 17 +++++++++++++++++
> > include/linux/virtio_ring.h | 2 ++
> > include/uapi/linux/virtio_config.h | 6 ++++++
> > 9 files changed, 56 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> > index a10dbe632ef9..d72a59415527 100644
> > --- a/drivers/s390/virtio/virtio_ccw.c
> > +++ b/drivers/s390/virtio/virtio_ccw.c
> > @@ -789,9 +789,7 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
> >
> > static void ccw_transport_features(struct virtio_device *vdev)
> > {
> > - /*
> > - * Currently nothing to do here.
> > - */
> > + __virtio_clear_bit(vdev, VIRTIO_F_NOTIFICATION_DATA);
>
> Is there any restriction that prevents us from implementing
> VIRTIO_F_NOTIFICATION_DATA? (Spec seems doesn't limit us from this)

Most likely, nothing.

>
> > }
> >
> > static int virtio_ccw_finalize_features(struct virtio_device *vdev)
> > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> > index 3ff746e3f24a..0e13da17fe0a 100644
> > --- a/drivers/virtio/virtio_mmio.c
> > +++ b/drivers/virtio/virtio_mmio.c
> > @@ -285,6 +285,19 @@ static bool vm_notify(struct virtqueue *vq)
> > return true;
> > }
> >
> > +static bool vm_notify_with_data(struct virtqueue *vq)
> > +{
> > + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
> > + u32 data = vring_fill_notification_data(vq);
>
> Can we move this to the initialization?

This data is new for each notification, because it helps to identify
the next available index.

>
> Thanks
>

Thanks,
Viktor Prutyanov