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

Michael S. Tsirkin
2023-03-21T12:22:44Z

On Tue, Mar 21, 2023 at 02:49:13PM +0300, Viktor Prutyanov wrote:
> On Tue, Mar 21, 2023 at 12:23 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Tue, Mar 21, 2023 at 02:21:15AM +0300, Viktor Prutyanov 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);
> > > }
> > >
> > > 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);
> > > +
> > > + writel(data, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
> > > +
> > > + return true;
> > > +}
> > > +
> > > +#define VM_NOTIFY(vdev) (__virtio_test_bit((vdev), VIRTIO_F_NOTIFICATION_DATA) \
> > > + ? vm_notify_with_data : vm_notify)
> > > +
> > > /* Notify all virtqueues on an interrupt. */
> > > static irqreturn_t vm_interrupt(int irq, void *opaque)
> > > {
> > > @@ -397,7 +410,7 @@ 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, VM_NOTIFY(vdev), callback, name);
> >
> > I don't see why is this macro useful.
> >
> >
> >
> > > 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..535263abc2bd 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_fill_notification_data(vq);
> > > +
> > > + iowrite32(data, (void __iomem *)vq->priv);
> > > +
> > > return true;
> > > }
> > >
> > > diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> > > index 23112d84218f..9a7212dcbb32 100644
> > > --- a/drivers/virtio/virtio_pci_common.h
> > > +++ b/drivers/virtio/virtio_pci_common.h
> > > @@ -105,6 +105,7 @@ static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
> > > void vp_synchronize_vectors(struct virtio_device *vdev);
> > > /* the notify function used when creating a virt queue */
> > > bool vp_notify(struct virtqueue *vq);
> > > +bool vp_notify_with_data(struct virtqueue *vq);
> > > /* the config->del_vqs() implementation */
> > > void vp_del_vqs(struct virtio_device *vdev);
> > > /* the config->find_vqs() implementation */
> > > @@ -114,6 +115,9 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
> > > struct irq_affinity *desc);
> > > const char *vp_bus_name(struct virtio_device *vdev);
> > >
> > > +#define VP_NOTIFY(vdev) (__virtio_test_bit((vdev), VIRTIO_F_NOTIFICATION_DATA) \
> > > + ? vp_notify : vp_notify_with_data)
> > > +
> > > /* Setup the affinity for a virtqueue:
> > > * - force the affinity for per vq vector
> > > * - OR over all affinities for shared MSI
> > > diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> > > index 2257f1b3d8ae..b98e994cae48 100644
> > > --- a/drivers/virtio/virtio_pci_legacy.c
> > > +++ b/drivers/virtio/virtio_pci_legacy.c
> > > @@ -131,7 +131,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> > > vq = vring_create_virtqueue(index, num,
> > > VIRTIO_PCI_VRING_ALIGN, &vp_dev->vdev,
> > > true, false, ctx,
> > > - vp_notify, callback, name);
> > > + VP_NOTIFY(&vp_dev->vdev), callback, name);
> > > if (!vq)
> > > return ERR_PTR(-ENOMEM);
> > >
> > > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > > index 9e496e288cfa..7fcd8af5af7e 100644
> > > --- a/drivers/virtio/virtio_pci_modern.c
> > > +++ b/drivers/virtio/virtio_pci_modern.c
> > > @@ -321,7 +321,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> > > vq = vring_create_virtqueue(index, num,
> > > SMP_CACHE_BYTES, &vp_dev->vdev,
> > > true, true, ctx,
> > > - vp_notify, callback, name);
> > > + VP_NOTIFY(&vp_dev->vdev), callback, name);
> > > if (!vq)
> > > return ERR_PTR(-ENOMEM);
> > >
> > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > index 723c4e29e1d3..5e9e1800bb6e 100644
> > > --- a/drivers/virtio/virtio_ring.c
> > > +++ b/drivers/virtio/virtio_ring.c
> > > @@ -2699,6 +2699,21 @@ void vring_del_virtqueue(struct virtqueue *_vq)
> > > }
> > > EXPORT_SYMBOL_GPL(vring_del_virtqueue);
> > >
> > > +u32 vring_fill_notification_data(struct virtqueue *_vq)
> > > +{
> > > + struct vring_virtqueue *vq = to_vvq(_vq);
> > > + u16 next;
> > > +
> > > + if (vq->packed_ring)
> > > + next = (vq->packed.next_avail_idx & ~(1 << 15)) |
> > > + ((u16)vq->packed.avail_wrap_counter << 15);
> >
> > I don't think the cast is needed. Neither is () around << the second <<
> > here (first is needed because gcc chooses to complain: apparently it
> > considers bitwise and a math operation for some obscure reason).
> >
> > > + else
> > > + next = virtio16_to_cpu(_vq->vdev, vq->split.vring.avail->idx);
> > > +
> > > + return ((u32)next << 16) | _vq->index;
> >
> > I don't think the cast is needed. Neither is () around << needed.
> >
> > > +}
> > > +EXPORT_SYMBOL_GPL(vring_fill_notification_data);
> > > +
> >
> > I'd inline this - it's on data path ...
>
> As far as I see, to be inlined in virtio_mmio.c, virtio_pci_common.c
> and virtio_ccw.c, the function should be defined in some header, but
> definitions such as vring_virtqueue, vring_virtqueue_split,
> vring_virtqueue_packed will not be available, because they are in
> virtio_ring.c. Looks like, they must be moved to a separate header
> in this case, isn't it?

Oh you are right. OK, sorry.

> >
> > > /* Manipulates transport-specific feature bits. */
> > > void vring_transport_features(struct virtio_device *vdev)
> > > {
> >
> > > @@ -2718,6 +2733,8 @@ void vring_transport_features(struct virtio_device *vdev)
> > > break;
> > > case VIRTIO_F_ORDER_PLATFORM:
> > > break;
> > > + case VIRTIO_F_NOTIFICATION_DATA:
> > > + break;
> > > default:
> > > /* We don't understand this bit. */
> > > __virtio_clear_bit(vdev, i);
> > > diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
> > > index 8b8af1a38991..1f65d2f77012 100644
> > > --- a/include/linux/virtio_ring.h
> > > +++ b/include/linux/virtio_ring.h
> > > @@ -101,4 +101,6 @@ void vring_del_virtqueue(struct virtqueue *vq);
> > > void vring_transport_features(struct virtio_device *vdev);
> > >
> > > irqreturn_t vring_interrupt(int irq, void *_vq);
> > > +
> > > +u32 vring_fill_notification_data(struct virtqueue *_vq);
> > > #endif /* _LINUX_VIRTIO_RING_H */
> > > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> > > index 3c05162bc988..2c712c654165 100644
> > > --- a/include/uapi/linux/virtio_config.h
> > > +++ b/include/uapi/linux/virtio_config.h
> > > @@ -99,6 +99,12 @@
> > > */
> > > #define VIRTIO_F_SR_IOV 37
> > >
> > > +/*
> > > + * This feature indicates that the driver passes extra data (besides
> > > + * identifying the virtqueue) in its device notifications.
> > > + */
> > > +#define VIRTIO_F_NOTIFICATION_DATA 38
> > > +
> > > /*
> > > * This feature indicates that the driver can reset a queue individually.
> > > */
> > > --
> > > 2.35.1
> >