Re: [RFC 1/8] virtio/virtio-pci: Handle extra notification data

[Jonah Palmer]

On 3/1/24 2:55 PM, Eugenio Perez Martin wrote:
> On Fri, Mar 1, 2024 at 2:44 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: last_avail_idx
> >   - lower 16 bits: virtqueue index
> >
> > In a packed virtqueue layout, this data includes:
> >   - upper 16 bits: 1-bit wrap counter & 15-bit last_avail_idx
> >   - lower 16 bits: virtqueue index
> >
> > Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
> > ---
> >   hw/virtio/virtio-pci.c     | 13 ++++++++++---
> >   hw/virtio/virtio.c         | 13 +++++++++++++
> >   include/hw/virtio/virtio.h |  1 +
> >   3 files changed, 24 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 1a7039fb0c..c7c577b177 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 +408,15 @@ 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);
> > +        if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
> > +            vq_idx = val & 0xFFFF;
> > +            virtio_set_notification_data(vdev, vq_idx, val);
> > +        } else {
> > +            vq_idx = val;
> > +        }
> > +
> > +        if (vq_idx < VIRTIO_QUEUE_MAX) {
> > +            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..a61f69b7fd 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -2052,6 +2052,19 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
> >       return 0;
> >   }
> >
> > +void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t 
> > data)
> > +{
> > +    VirtQueue *vq = &vdev->vq[i];
>
> Sorry I sent the previous mail too fast :).
>
> i should also be checked against VIRTIO_QUEUE_MAX and vq->vring.desc
> before continuing this function. Otherwise is an out of bound access.

Missed this, thank you. I will add these checks in!

> > +
> > +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> > +        vq->last_avail_wrap_counter = (data >> 31) & 0x1;
> > +        vq->last_avail_idx = (data >> 16) & 0x7FFF;
> > +    } else {
> > +        vq->last_avail_idx = (data >> 16) & 0xFFFF;
> > +    }
> > +    vq->shadow_avail_idx = vq->last_avail_idx;
> > +}
> > +
> >   static enum virtio_device_endian virtio_default_endian(void)
> >   {
> >       if (target_words_bigendian()) {
> > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > index c8f72850bc..c92d8afc42 100644
> > --- a/include/hw/virtio/virtio.h
> > +++ b/include/hw/virtio/virtio.h
> > @@ -345,6 +345,7 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t 
> > queue_index);
> >   void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
> >   void virtio_update_irq(VirtIODevice *vdev);
> >   int virtio_set_features(VirtIODevice *vdev, uint64_t val);
> > +void virtio_set_notification_data(VirtIODevice *vdev, uint16_t i, uint32_t 
> > data);
> >
> >   /* Base devices.  */
> >   typedef struct VirtIOBlkConf VirtIOBlkConf;
> > --
> > 2.39.3