This patch implements virtio pci support for QUEUE RESET.

Performing reset on a queue is divided into two steps:

1. reset_vq: reset one vq
2. enable_reset_vq: re-enable the reset queue

In the first step, these tasks will be completed:
    1. notify the hardware queue to reset
    2. recycle the buffer from vq
    3. release the ring of the vq

The process of enable reset vq:
     vp_modern_enable_reset_vq()
     vp_enable_reset_vq()
     __vp_setup_vq()
     setup_vq()
     vring_setup_virtqueue()

In this process, we added two parameters, vq and num, and finally passed
them to vring_setup_virtqueue().  And reuse the original info and vq.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
  drivers/virtio/virtio_pci_common.c |  36 +++++++----
  drivers/virtio/virtio_pci_common.h |   5 ++
  drivers/virtio/virtio_pci_modern.c | 100 +++++++++++++++++++++++++++++
  3 files changed, 128 insertions(+), 13 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index c02936d29a31..ad21638fbf66 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c

@@ -205,23 +205,28 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
  	return err;
  }
  
-static struct virtqueue *vp_setup_vq(struct virtio_device *vdev, unsigned index,
-				     void (*callback)(struct virtqueue *vq),
-				     const char *name,
-				     bool ctx,
-				     u16 msix_vec, u16 num)
+struct virtqueue *vp_setup_vq(struct virtio_device *vdev, unsigned index,
+			      void (*callback)(struct virtqueue *vq),
+			      const char *name,
+			      bool ctx,
+			      u16 msix_vec, u16 num)
  {
  	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-	struct virtio_pci_vq_info *info = kmalloc(sizeof *info, GFP_KERNEL);
+	struct virtio_pci_vq_info *info;
  	struct virtqueue *vq;
  	unsigned long flags;
  
-	/* fill out our structure that represents an active queue */
-	if (!info)
-		return ERR_PTR(-ENOMEM);
+	info = vp_dev->vqs[index];
+	if (!info) {
+		info = kzalloc(sizeof *info, GFP_KERNEL);
+
+		/* fill out our structure that represents an active queue */
+		if (!info)
+			return ERR_PTR(-ENOMEM);
+	}
  
  	vq = vp_dev->setup_vq(vp_dev, info, index, callback, name, ctx,
-			      msix_vec, NULL, num);
+			      msix_vec, info->vq, num);
  	if (IS_ERR(vq))
  		goto out_info;
  

@@ -238,6 +243,9 @@ static struct virtqueue *vp_setup_vq(struct virtio_device *vdev, unsigned index,
  	return vq;
  
  out_info:
+	if (info->vq && info->vq->reset)
+		return vq;
+
  	kfree(info);
  	return vq;
  }

@@ -248,9 +256,11 @@ static void vp_del_vq(struct virtqueue *vq)
  	struct virtio_pci_vq_info *info = vp_dev->vqs[vq->index];
  	unsigned long flags;
  
-	spin_lock_irqsave(&vp_dev->lock, flags);
-	list_del(&info->node);
-	spin_unlock_irqrestore(&vp_dev->lock, flags);
+	if (!vq->reset) {
+		spin_lock_irqsave(&vp_dev->lock, flags);
+		list_del(&info->node);
+		spin_unlock_irqrestore(&vp_dev->lock, flags);
+	}
  
  	vp_dev->del_vq(info);
  	kfree(info);

diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index 65db92245e41..c1d15f7c0be4 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h

@@ -119,6 +119,11 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
  		struct virtqueue *vqs[], vq_callback_t *callbacks[],
  		const char * const names[], const bool *ctx,
  		struct irq_affinity *desc);
+struct virtqueue *vp_setup_vq(struct virtio_device *vdev, unsigned index,
+			      void (*callback)(struct virtqueue *vq),
+			      const char *name,
+			      bool ctx,
+			      u16 msix_vec, u16 num);
  const char *vp_bus_name(struct virtio_device *vdev);
  
  /* Setup the affinity for a virtqueue:

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 2ce58de549de..6789411169e4 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c

@@ -34,6 +34,9 @@ static void vp_transport_features(struct virtio_device *vdev, u64 features)
  	if ((features & BIT_ULL(VIRTIO_F_SR_IOV)) &&
  			pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_SRIOV))
  		__virtio_set_bit(vdev, VIRTIO_F_SR_IOV);
+
+	if (features & BIT_ULL(VIRTIO_F_RING_RESET))
+		__virtio_set_bit(vdev, VIRTIO_F_RING_RESET);
  }
  
  /* virtio config->finalize_features() implementation */

@@ -176,6 +179,94 @@ static void vp_reset(struct virtio_device *vdev)
  	vp_disable_cbs(vdev);
  }
  
+static int vp_modern_reset_vq(struct virtio_reset_vq *param)
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(param->vdev);
+	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
+	struct virtio_pci_vq_info *info;
+	u16 msix_vec, queue_index;
+	unsigned long flags;
+	void *buf;
+
+	if (!virtio_has_feature(param->vdev, VIRTIO_F_RING_RESET))
+		return -ENOENT;
+
+	queue_index = param->queue_index;
+
+	vp_modern_set_queue_reset(mdev, queue_index);
+
+	/* After write 1 to queue reset, the driver MUST wait for a read of
+	 * queue reset to return 1.
+	 */
+	while (vp_modern_get_queue_reset(mdev, queue_index) != 1)
+		msleep(1);

+
+	return vq;
+}
+
  static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
  {
  	return vp_modern_config_vector(&vp_dev->mdev, vector);

@@ -284,6 +375,11 @@ static void del_vq(struct virtio_pci_vq_info *info)
  	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
  	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
  
+	if (vq->reset) {
+		vring_del_virtqueue(vq);
+		return;
+	}
+
  	if (vp_dev->msix_enabled)
  		vp_modern_queue_vector(mdev, vq->index,
  				       VIRTIO_MSI_NO_VECTOR);

@@ -403,6 +499,8 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
  	.set_vq_affinity = vp_set_vq_affinity,
  	.get_vq_affinity = vp_get_vq_affinity,
  	.get_shm_region  = vp_get_shm_region,
+	.reset_vq	 = vp_modern_reset_vq,
+	.enable_reset_vq = vp_modern_enable_reset_vq,
  };
  
  static const struct virtio_config_ops virtio_pci_config_ops = {

@@ -421,6 +519,8 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
  	.set_vq_affinity = vp_set_vq_affinity,
  	.get_vq_affinity = vp_get_vq_affinity,
  	.get_shm_region  = vp_get_shm_region,
+	.reset_vq	 = vp_modern_reset_vq,
+	.enable_reset_vq = vp_modern_enable_reset_vq,
  };
  
  /* the PCI probing function */