Re: [PATCH v6] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

From: Viktor Prutyanov
Date: Wed Mar 29 2023 - 18:49:41 EST

On Fri, Mar 24, 2023 at 10:50 PM Viktor Prutyanov <viktor@xxxxxxxxxx> 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, channel I/O and modern PCI
> transports.
>
> Signed-off-by: Viktor Prutyanov <viktor@xxxxxxxxxx>
> Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> v6: use VRING_PACKED_EVENT_F_WRAP_CTR
> v5: replace ternary operator with if-else
> v4: remove VP_NOTIFY macro and legacy PCI support, add
> virtio_ccw_kvm_notify_with_data to virtio_ccw
> 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
>
> Tested with disabled VIRTIO_F_NOTIFICATION_DATA on qemu-system-s390x
> (virtio-blk-ccw), qemu-system-riscv64 (virtio-blk-device,
> virtio-rng-device), qemu-system-x86_64 (virtio-blk-pci, virtio-net-pci)
> to make sure nothing is broken.
> Tested with enabled VIRTIO_F_NOTIFICATION_DATA on 64-bit RISC-V Linux
> and my hardware implementation of virtio-rng with MMIO.
>
> drivers/s390/virtio/virtio_ccw.c | 22 +++++++++++++++++++---
> drivers/virtio/virtio_mmio.c | 18 +++++++++++++++++-
> drivers/virtio/virtio_pci_modern.c | 17 ++++++++++++++++-
> drivers/virtio/virtio_ring.c | 19 +++++++++++++++++++
> include/linux/virtio_ring.h | 2 ++
> include/uapi/linux/virtio_config.h | 6 ++++++
> 6 files changed, 79 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 954fc31b4bc7..02922768b129 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -391,7 +391,7 @@ static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev,
> ccw_device_dma_free(vcdev->cdev, thinint_area, sizeof(*thinint_area));
> }
>
> -static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
> +static inline bool virtio_ccw_do_kvm_notify(struct virtqueue *vq, u32 data)
> {
> struct virtio_ccw_vq_info *info = vq->priv;
> struct virtio_ccw_device *vcdev;
> @@ -402,12 +402,22 @@ static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
> 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;
> }
>
> +static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
> +{
> + return virtio_ccw_do_kvm_notify(vq, vq->index);
> +}
> +
> +static bool virtio_ccw_kvm_notify_with_data(struct virtqueue *vq)
> +{
> + return virtio_ccw_do_kvm_notify(vq, vring_notification_data(vq));
> +}
> +
> static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
> struct ccw1 *ccw, int index)
> {
> @@ -495,6 +505,7 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
> struct ccw1 *ccw)
> {
> struct virtio_ccw_device *vcdev = to_vc_device(vdev);
> + bool (*notify)(struct virtqueue *vq);
> int err;
> struct virtqueue *vq = NULL;
> struct virtio_ccw_vq_info *info;
> @@ -502,6 +513,11 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
> unsigned long flags;
> bool may_reduce;
>
> + if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA))
> + notify = virtio_ccw_kvm_notify_with_data;
> + else
> + notify = virtio_ccw_kvm_notify;
> +
> /* Allocate queue. */
> info = kzalloc(sizeof(struct virtio_ccw_vq_info), GFP_KERNEL);
> if (!info) {
> @@ -524,7 +540,7 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
> may_reduce = vcdev->revision > 0;
> vq = vring_create_virtqueue(i, info->num, KVM_VIRTIO_CCW_RING_ALIGN,
> vdev, true, may_reduce, ctx,
> - virtio_ccw_kvm_notify, callback, name);
> + notify, callback, name);
>
> if (!vq) {
> /* For now, we fail if we can't get the requested size. */
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 3ff746e3f24a..dd4424c14233 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);
> +
> + return true;
> +}
> +
> /* Notify all virtqueues on an interrupt. */
> static irqreturn_t vm_interrupt(int irq, void *opaque)
> {
> @@ -363,12 +373,18 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
> const char *name, bool ctx)
> {
> struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
> + bool (*notify)(struct virtqueue *vq);
> struct virtio_mmio_vq_info *info;
> struct virtqueue *vq;
> unsigned long flags;
> unsigned int num;
> int err;
>
> + if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA))
> + notify = vm_notify_with_data;
> + else
> + notify = vm_notify;
> +
> if (!name)
> return NULL;
>
> @@ -397,7 +413,7 @@ 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_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 9e496e288cfa..05deba5153bd 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -288,6 +288,15 @@ static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
> return vp_modern_config_vector(&vp_dev->mdev, vector);
> }
>
> +static bool vp_notify_with_data(struct virtqueue *vq)
> +{
> + u32 data = vring_notification_data(vq);
> +
> + iowrite32(data, (void __iomem *)vq->priv);
> +
> + return true;
> +}
> +
> static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> struct virtio_pci_vq_info *info,
> unsigned int index,
> @@ -298,10 +307,16 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> {
>
> struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> + bool (*notify)(struct virtqueue *vq);
> struct virtqueue *vq;
> u16 num;
> int err;
>
> + if (__virtio_test_bit(&vp_dev->vdev, VIRTIO_F_NOTIFICATION_DATA))
> + notify = vp_notify_with_data;
> + else
> + notify = vp_notify;
> +
> if (index >= vp_modern_get_num_queues(mdev))
> return ERR_PTR(-EINVAL);
>
> @@ -321,7 +336,7 @@ 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);
> + notify, callback, name);
> if (!vq)
> return ERR_PTR(-ENOMEM);
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 4c3bb0ddeb9b..f9c6604352b4 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2752,6 +2752,23 @@ void vring_del_virtqueue(struct virtqueue *_vq)
> }
> EXPORT_SYMBOL_GPL(vring_del_virtqueue);
>
> +u32 vring_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 << VRING_PACKED_EVENT_F_WRAP_CTR))) |
> + vq->packed.avail_wrap_counter <<
> + VRING_PACKED_EVENT_F_WRAP_CTR;
> + else
> + next = vq->split.avail_idx_shadow;
> +
> + return next << 16 | _vq->index;
> +}
> +EXPORT_SYMBOL_GPL(vring_notification_data);
> +
> /* Manipulates transport-specific feature bits. */
> void vring_transport_features(struct virtio_device *vdev)
> {
> @@ -2771,6 +2788,8 @@ 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 8b95b69ef694..2550c9170f4f 100644
> --- a/include/linux/virtio_ring.h
> +++ b/include/linux/virtio_ring.h
> @@ -117,4 +117,6 @@ 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_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
>

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