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Date:   Wed, 22 Mar 2023 12:33:40 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Viktor Prutyanov <viktor@daynix.com>
Cc:     jasowang@redhat.com, cohuck@redhat.com, pasic@linux.ibm.com,
        farman@linux.ibm.com, linux-s390@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, yan@daynix.com
Subject: Re: [PATCH v4] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support
Message-ID: <20230322123121-mutt-send-email-mst@kernel.org>
References: <20230322141031.2211141-1-viktor@daynix.com>
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On Wed, Mar 22, 2023 at 05:10:31PM +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, channel I/O and modern PCI
> transports.
> 
> Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
> ---
>  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.

what did you test? virtio pci? mmio? guessing not ccw...

Cornelia could you hack up something to quickly test ccw?

>  drivers/s390/virtio/virtio_ccw.c   | 19 ++++++++++++++++---
>  drivers/virtio/virtio_mmio.c       | 14 +++++++++++++-
>  drivers/virtio/virtio_pci_modern.c | 13 ++++++++++++-
>  drivers/virtio/virtio_ring.c       | 17 +++++++++++++++++
>  include/linux/virtio_ring.h        |  2 ++
>  include/uapi/linux/virtio_config.h |  6 ++++++
>  6 files changed, 66 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 954fc31b4bc7..3619676effb8 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)
>  {
> @@ -501,6 +511,9 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
>  	u64 queue;
>  	unsigned long flags;
>  	bool may_reduce;
> +	bool (*notify)(struct virtqueue *vq) = __virtio_test_bit(vdev,
> +		VIRTIO_F_NOTIFICATION_DATA) ?
> +		virtio_ccw_kvm_notify_with_data : virtio_ccw_kvm_notify;
>  
>  	/* Allocate queue. */
>  	info = kzalloc(sizeof(struct virtio_ccw_vq_info), GFP_KERNEL);
> @@ -524,7 +537,7 @@ 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..7c16e622c33d 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.cv
> @@ -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)
>  {
> @@ -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_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 9e496e288cfa..9cc56f463dba 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,
> @@ -301,6 +310,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  	struct virtqueue *vq;
>  	u16 num;
>  	int err;
> +	bool (*notify)(struct virtqueue *vq) = __virtio_test_bit(&vp_dev->vdev,
> +		VIRTIO_F_NOTIFICATION_DATA) ? vp_notify_with_data : vp_notify;
>  
>  	if (index >= vp_modern_get_num_queues(mdev))
>  		return ERR_PTR(-EINVAL);
> @@ -321,7 +332,7 @@ 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..837875cc3190 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2752,6 +2752,21 @@ 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 << 15)) |
> +			vq->packed.avail_wrap_counter << 15;
> +	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 +2786,8 @@ 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