Re: [PATCH v3] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

Cornelia Huck
2023-03-21T15:00:01Z

On Tue, Mar 21 2023, 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, PCI and channel I/O transports.
>
> Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
> ---
> v3: support feature in virtio_ccw, remove VM_NOTIFY, use avail_idx_shadow,
> remove byte swap, rename to vring_notification_data
> v2: reject the feature in virtio_ccw, replace __le32 with u32
>
> drivers/s390/virtio/virtio_ccw.c | 4 +++-
> drivers/virtio/virtio_mmio.c | 14 +++++++++++++-
> 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, 57 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 954fc31b4bc7..c33172c5b8d5 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -396,13 +396,15 @@ static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
> struct virtio_ccw_vq_info *info = vq->priv;
> struct virtio_ccw_device *vcdev;
> struct subchannel_id schid;
> + u32 data = __virtio_test_bit(vq->vdev, VIRTIO_F_NOTIFICATION_DATA) ?
> + vring_notification_data(vq) : vq->index;
>
> vcdev = to_vc_device(info->vq->vdev);
> ccw_device_get_schid(vcdev->cdev, &schid);
> BUILD_BUG_ON(sizeof(struct subchannel_id) != sizeof(unsigned int));
> info->cookie = kvm_hypercall3(KVM_S390_VIRTIO_CCW_NOTIFY,
> *((unsigned int *)&schid),
> - vq->index, info->cookie);
> + data, info->cookie);
> if (info->cookie < 0)
> return false;
> return true;
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 3ff746e3f24a..7c16e622c33d 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -285,6 +285,16 @@ 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_notification_data(vq);
> +
> + writel(data, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);

Can't you simply use the same method as for ccw, i.e. use one callback
function that simply writes one value or the other?

> +
> + return true;
> +}
> +
> /* Notify all virtqueues on an interrupt. */
> static irqreturn_t vm_interrupt(int irq, void *opaque)
> {
> @@ -368,6 +378,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
> unsigned long flags;
> unsigned int num;
> int err;
> + bool (*notify)(struct virtqueue *vq) = __virtio_test_bit(vdev,
> + VIRTIO_F_NOTIFICATION_DATA) ? vm_notify_with_data : vm_notify;
>
> if (!name)
> return NULL;
> @@ -397,7 +409,7 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
>
> /* Create the vring */
> vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,
> - true, true, ctx, vm_notify, callback, name);
> + true, true, ctx, notify, callback, name);
> if (!vq) {
> err = -ENOMEM;
> goto error_new_virtqueue;
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index a6c86f916dbd..e915c22f2384 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -43,6 +43,16 @@ bool vp_notify(struct virtqueue *vq)
> /* we write the queue's selector into the notification register to
> * signal the other end */
> iowrite16(vq->index, (void __iomem *)vq->priv);
> +
> + return true;
> +}
> +
> +bool vp_notify_with_data(struct virtqueue *vq)
> +{
> + u32 data = vring_notification_data(vq);
> +
> + iowrite32(data, (void __iomem *)vq->priv);

Same for pci.

> +
> return true;
> }
>