[PATCH v3] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

[Viktor Prutyanov <viktor@daynix.com>]

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);
+
+	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);
+
 	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 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