Re: [PATCH v2 1/6] virtio/virtio-pci: Handle extra notification data

[Eugenio Perez Martin <eperezma@redhat.com>]

On Thu, Mar 14, 2024 at 1:16 PM Jonah Palmer <jonah.palmer@oracle.com> wrote:
>
>
>
> On 3/13/24 11:01 PM, Jason Wang wrote:
> > On Wed, Mar 13, 2024 at 7:55 PM Jonah Palmer <jonah.palmer@oracle.com> wrote:
> >>
> >> Add support to virtio-pci devices for handling the extra data sent
> >> from the driver to the device when the VIRTIO_F_NOTIFICATION_DATA
> >> transport feature has been negotiated.
> >>
> >> The extra data that's passed to the virtio-pci device when this
> >> feature is enabled varies depending on the device's virtqueue
> >> layout.
> >>
> >> In a split virtqueue layout, this data includes:
> >>   - upper 16 bits: shadow_avail_idx
> >>   - lower 16 bits: virtqueue index
> >>
> >> In a packed virtqueue layout, this data includes:
> >>   - upper 16 bits: 1-bit wrap counter & 15-bit shadow_avail_idx
> >>   - lower 16 bits: virtqueue index
> >>
> >> Tested-by: Lei Yang <leiyang@redhat.com>
> >> Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
> >> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
> >> ---
> >>   hw/virtio/virtio-pci.c     | 10 +++++++---
> >>   hw/virtio/virtio.c         | 18 ++++++++++++++++++
> >>   include/hw/virtio/virtio.h |  1 +
> >>   3 files changed, 26 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index cb6940fc0e..0f5c3c3b2f 100644
> >> --- a/hw/virtio/virtio-pci.c
> >> +++ b/hw/virtio/virtio-pci.c
> >> @@ -384,7 +384,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> >>   {
> >>       VirtIOPCIProxy *proxy = opaque;
> >>       VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> >> -    uint16_t vector;
> >> +    uint16_t vector, vq_idx;
> >>       hwaddr pa;
> >>
> >>       switch (addr) {
> >> @@ -408,8 +408,12 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> >>               vdev->queue_sel = val;
> >>           break;
> >>       case VIRTIO_PCI_QUEUE_NOTIFY:
> >> -        if (val < VIRTIO_QUEUE_MAX) {
> >> -            virtio_queue_notify(vdev, val);
> >> +        vq_idx = val;
> >> +        if (vq_idx < VIRTIO_QUEUE_MAX) {
> >> +            if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
> >> +                virtio_queue_set_shadow_avail_data(vdev, val);
> >> +            }
> >> +            virtio_queue_notify(vdev, vq_idx);
> >>           }
> >>           break;
> >>       case VIRTIO_PCI_STATUS:
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index d229755eae..bcb9e09df0 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -2255,6 +2255,24 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
> >>       }
> >>   }
> >>
> >> +void virtio_queue_set_shadow_avail_data(VirtIODevice *vdev, uint32_t data)

Maybe I didn't explain well, but I think it is better to pass directly
idx to a VirtQueue *. That way only the caller needs to check for a
valid vq idx, and (my understanding is) the virtio.c interface is
migrating to VirtQueue * use anyway.

> >> +{
> >> +    /* Lower 16 bits is the virtqueue index */
> >> +    uint16_t i = data;
> >> +    VirtQueue *vq = &vdev->vq[i];
> >> +
> >> +    if (!vq->vring.desc) {
> >> +        return;
> >> +    }
> >> +
> >> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >> +        vq->shadow_avail_wrap_counter = (data >> 31) & 0x1;
> >> +        vq->shadow_avail_idx = (data >> 16) & 0x7FFF;
> >> +    } else {
> >> +        vq->shadow_avail_idx = (data >> 16);
> >
> > Do we need to do a sanity check for this value?
> >
> > Thanks
> >
>
> It can't hurt, right? What kind of check did you have in mind?
>
> if (vq->shadow_avail_idx >= vq->vring.num)
>

I'm a little bit lost too. shadow_avail_idx can take all uint16_t
values. Maybe you meant checking for a valid vq index, Jason?

Thanks!

> Or something else?
>
> >> +    }
> >> +}
> >> +
> >>   static void virtio_queue_notify_vq(VirtQueue *vq)
> >>   {
> >>       if (vq->vring.desc && vq->handle_output) {
> >> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >> index c8f72850bc..53915947a7 100644
> >> --- a/include/hw/virtio/virtio.h
> >> +++ b/include/hw/virtio/virtio.h
> >> @@ -335,6 +335,7 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n);
> >>   void virtio_init_region_cache(VirtIODevice *vdev, int n);
> >>   void virtio_queue_set_align(VirtIODevice *vdev, int n, int align);
> >>   void virtio_queue_notify(VirtIODevice *vdev, int n);
> >> +void virtio_queue_set_shadow_avail_data(VirtIODevice *vdev, uint32_t data);
> >>   uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);
> >>   void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector);
> >>   int virtio_queue_set_host_notifier_mr(VirtIODevice *vdev, int n,
> >> --
> >> 2.39.3
> >>
> >
>