diff mbox series

[v11,01/40] virtio: add helper virtqueue_get_vring_max_size()

Message ID 20220629065656.54420-2-xuanzhuo@linux.alibaba.com (mailing list archive)
State Not Applicable
Delegated to: Netdev Maintainers
Headers show
Series virtio pci support VIRTIO_F_RING_RESET | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply

Commit Message

Xuan Zhuo June 29, 2022, 6:56 a.m. UTC
Record the maximum queue num supported by the device.

virtio-net can display the maximum (supported by hardware) ring size in
ethtool -g eth0.

When the subsequent patch implements vring reset, it can judge whether
the ring size passed by the driver is legal based on this.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 arch/um/drivers/virtio_uml.c             |  1 +
 drivers/platform/mellanox/mlxbf-tmfifo.c |  2 ++
 drivers/remoteproc/remoteproc_virtio.c   |  2 ++
 drivers/s390/virtio/virtio_ccw.c         |  3 +++
 drivers/virtio/virtio_mmio.c             |  2 ++
 drivers/virtio/virtio_pci_legacy.c       |  2 ++
 drivers/virtio/virtio_pci_modern.c       |  2 ++
 drivers/virtio/virtio_ring.c             | 14 ++++++++++++++
 drivers/virtio/virtio_vdpa.c             |  2 ++
 include/linux/virtio.h                   |  2 ++
 10 files changed, 32 insertions(+)

Comments

Jason Wang June 30, 2022, 6:35 a.m. UTC | #1
On Wed, Jun 29, 2022 at 2:57 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> Record the maximum queue num supported by the device.
>
> virtio-net can display the maximum (supported by hardware) ring size in
> ethtool -g eth0.
>
> When the subsequent patch implements vring reset, it can judge whether
> the ring size passed by the driver is legal based on this.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  arch/um/drivers/virtio_uml.c             |  1 +
>  drivers/platform/mellanox/mlxbf-tmfifo.c |  2 ++
>  drivers/remoteproc/remoteproc_virtio.c   |  2 ++
>  drivers/s390/virtio/virtio_ccw.c         |  3 +++
>  drivers/virtio/virtio_mmio.c             |  2 ++
>  drivers/virtio/virtio_pci_legacy.c       |  2 ++
>  drivers/virtio/virtio_pci_modern.c       |  2 ++
>  drivers/virtio/virtio_ring.c             | 14 ++++++++++++++
>  drivers/virtio/virtio_vdpa.c             |  2 ++
>  include/linux/virtio.h                   |  2 ++
>  10 files changed, 32 insertions(+)
>
> diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
> index 82ff3785bf69..e719af8bdf56 100644
> --- a/arch/um/drivers/virtio_uml.c
> +++ b/arch/um/drivers/virtio_uml.c
> @@ -958,6 +958,7 @@ static struct virtqueue *vu_setup_vq(struct virtio_device *vdev,
>                 goto error_create;
>         }
>         vq->priv = info;
> +       vq->num_max = num;
>         num = virtqueue_get_vring_size(vq);
>
>         if (vu_dev->protocol_features &
> diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
> index 38800e86ed8a..1ae3c56b66b0 100644
> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> @@ -959,6 +959,8 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
>                         goto error;
>                 }
>
> +               vq->num_max = vring->num;
> +
>                 vqs[i] = vq;
>                 vring->vq = vq;
>                 vq->priv = vring;
> diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> index d43d74733f0a..0f7706e23eb9 100644
> --- a/drivers/remoteproc/remoteproc_virtio.c
> +++ b/drivers/remoteproc/remoteproc_virtio.c
> @@ -125,6 +125,8 @@ static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
>                 return ERR_PTR(-ENOMEM);
>         }
>
> +       vq->num_max = num;
> +
>         rvring->vq = vq;
>         vq->priv = rvring;
>
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index 161d3b141f0d..6b86d0280d6b 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -530,6 +530,9 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
>                 err = -ENOMEM;
>                 goto out_err;
>         }
> +
> +       vq->num_max = info->num;
> +
>         /* it may have been reduced */
>         info->num = virtqueue_get_vring_size(vq);
>
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 083ff1eb743d..a20d5a6b5819 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -403,6 +403,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
>                 goto error_new_virtqueue;
>         }
>
> +       vq->num_max = num;
> +
>         /* Activate the queue */
>         writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
>         if (vm_dev->version == 1) {
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index a5e5721145c7..2257f1b3d8ae 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -135,6 +135,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>         if (!vq)
>                 return ERR_PTR(-ENOMEM);
>
> +       vq->num_max = num;
> +
>         q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
>         if (q_pfn >> 32) {
>                 dev_err(&vp_dev->pci_dev->dev,
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 623906b4996c..e7e0b8c850f6 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -218,6 +218,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>         if (!vq)
>                 return ERR_PTR(-ENOMEM);
>
> +       vq->num_max = num;
> +
>         /* activate the queue */
>         vp_modern_set_queue_size(mdev, index, virtqueue_get_vring_size(vq));
>         vp_modern_queue_address(mdev, index, virtqueue_get_desc_addr(vq),
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index a5ec724c01d8..4cac600856ad 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2385,6 +2385,20 @@ void vring_transport_features(struct virtio_device *vdev)
>  }
>  EXPORT_SYMBOL_GPL(vring_transport_features);
>
> +/**
> + * virtqueue_get_vring_max_size - return the max size of the virtqueue's vring
> + * @_vq: the struct virtqueue containing the vring of interest.
> + *
> + * Returns the max size of the vring.
> + *
> + * Unlike other operations, this need not be serialized.
> + */
> +unsigned int virtqueue_get_vring_max_size(struct virtqueue *_vq)
> +{
> +       return _vq->num_max;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_get_vring_max_size);
> +
>  /**
>   * virtqueue_get_vring_size - return the size of the virtqueue's vring
>   * @_vq: the struct virtqueue containing the vring of interest.
> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> index c40f7deb6b5a..9670cc79371d 100644
> --- a/drivers/virtio/virtio_vdpa.c
> +++ b/drivers/virtio/virtio_vdpa.c
> @@ -183,6 +183,8 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
>                 goto error_new_virtqueue;
>         }
>
> +       vq->num_max = max_num;
> +
>         /* Setup virtqueue callback */
>         cb.callback = callback ? virtio_vdpa_virtqueue_cb : NULL;
>         cb.private = info;
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index d8fdf170637c..a82620032e43 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -31,6 +31,7 @@ struct virtqueue {
>         struct virtio_device *vdev;
>         unsigned int index;
>         unsigned int num_free;
> +       unsigned int num_max;

A question, since we export virtqueue to drivers, this means they can
access vq->num_max directly.

So we probably don't need a helper here.

Thanks

>         void *priv;
>  };
>
> @@ -80,6 +81,7 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
>
>  void *virtqueue_detach_unused_buf(struct virtqueue *vq);
>
> +unsigned int virtqueue_get_vring_max_size(struct virtqueue *vq);
>  unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
>
>  bool virtqueue_is_broken(struct virtqueue *vq);
> --
> 2.31.0
>
Xuan Zhuo July 1, 2022, 6:43 a.m. UTC | #2
On Thu, 30 Jun 2022 14:35:38 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Wed, Jun 29, 2022 at 2:57 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > Record the maximum queue num supported by the device.
> >
> > virtio-net can display the maximum (supported by hardware) ring size in
> > ethtool -g eth0.
> >
> > When the subsequent patch implements vring reset, it can judge whether
> > the ring size passed by the driver is legal based on this.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >  arch/um/drivers/virtio_uml.c             |  1 +
> >  drivers/platform/mellanox/mlxbf-tmfifo.c |  2 ++
> >  drivers/remoteproc/remoteproc_virtio.c   |  2 ++
> >  drivers/s390/virtio/virtio_ccw.c         |  3 +++
> >  drivers/virtio/virtio_mmio.c             |  2 ++
> >  drivers/virtio/virtio_pci_legacy.c       |  2 ++
> >  drivers/virtio/virtio_pci_modern.c       |  2 ++
> >  drivers/virtio/virtio_ring.c             | 14 ++++++++++++++
> >  drivers/virtio/virtio_vdpa.c             |  2 ++
> >  include/linux/virtio.h                   |  2 ++
> >  10 files changed, 32 insertions(+)
> >
> > diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
> > index 82ff3785bf69..e719af8bdf56 100644
> > --- a/arch/um/drivers/virtio_uml.c
> > +++ b/arch/um/drivers/virtio_uml.c
> > @@ -958,6 +958,7 @@ static struct virtqueue *vu_setup_vq(struct virtio_device *vdev,
> >                 goto error_create;
> >         }
> >         vq->priv = info;
> > +       vq->num_max = num;
> >         num = virtqueue_get_vring_size(vq);
> >
> >         if (vu_dev->protocol_features &
> > diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
> > index 38800e86ed8a..1ae3c56b66b0 100644
> > --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> > +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> > @@ -959,6 +959,8 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
> >                         goto error;
> >                 }
> >
> > +               vq->num_max = vring->num;
> > +
> >                 vqs[i] = vq;
> >                 vring->vq = vq;
> >                 vq->priv = vring;
> > diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> > index d43d74733f0a..0f7706e23eb9 100644
> > --- a/drivers/remoteproc/remoteproc_virtio.c
> > +++ b/drivers/remoteproc/remoteproc_virtio.c
> > @@ -125,6 +125,8 @@ static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
> >                 return ERR_PTR(-ENOMEM);
> >         }
> >
> > +       vq->num_max = num;
> > +
> >         rvring->vq = vq;
> >         vq->priv = rvring;
> >
> > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> > index 161d3b141f0d..6b86d0280d6b 100644
> > --- a/drivers/s390/virtio/virtio_ccw.c
> > +++ b/drivers/s390/virtio/virtio_ccw.c
> > @@ -530,6 +530,9 @@ static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
> >                 err = -ENOMEM;
> >                 goto out_err;
> >         }
> > +
> > +       vq->num_max = info->num;
> > +
> >         /* it may have been reduced */
> >         info->num = virtqueue_get_vring_size(vq);
> >
> > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> > index 083ff1eb743d..a20d5a6b5819 100644
> > --- a/drivers/virtio/virtio_mmio.c
> > +++ b/drivers/virtio/virtio_mmio.c
> > @@ -403,6 +403,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
> >                 goto error_new_virtqueue;
> >         }
> >
> > +       vq->num_max = num;
> > +
> >         /* Activate the queue */
> >         writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
> >         if (vm_dev->version == 1) {
> > diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> > index a5e5721145c7..2257f1b3d8ae 100644
> > --- a/drivers/virtio/virtio_pci_legacy.c
> > +++ b/drivers/virtio/virtio_pci_legacy.c
> > @@ -135,6 +135,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> >         if (!vq)
> >                 return ERR_PTR(-ENOMEM);
> >
> > +       vq->num_max = num;
> > +
> >         q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
> >         if (q_pfn >> 32) {
> >                 dev_err(&vp_dev->pci_dev->dev,
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 623906b4996c..e7e0b8c850f6 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -218,6 +218,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> >         if (!vq)
> >                 return ERR_PTR(-ENOMEM);
> >
> > +       vq->num_max = num;
> > +
> >         /* activate the queue */
> >         vp_modern_set_queue_size(mdev, index, virtqueue_get_vring_size(vq));
> >         vp_modern_queue_address(mdev, index, virtqueue_get_desc_addr(vq),
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index a5ec724c01d8..4cac600856ad 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2385,6 +2385,20 @@ void vring_transport_features(struct virtio_device *vdev)
> >  }
> >  EXPORT_SYMBOL_GPL(vring_transport_features);
> >
> > +/**
> > + * virtqueue_get_vring_max_size - return the max size of the virtqueue's vring
> > + * @_vq: the struct virtqueue containing the vring of interest.
> > + *
> > + * Returns the max size of the vring.
> > + *
> > + * Unlike other operations, this need not be serialized.
> > + */
> > +unsigned int virtqueue_get_vring_max_size(struct virtqueue *_vq)
> > +{
> > +       return _vq->num_max;
> > +}
> > +EXPORT_SYMBOL_GPL(virtqueue_get_vring_max_size);
> > +
> >  /**
> >   * virtqueue_get_vring_size - return the size of the virtqueue's vring
> >   * @_vq: the struct virtqueue containing the vring of interest.
> > diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
> > index c40f7deb6b5a..9670cc79371d 100644
> > --- a/drivers/virtio/virtio_vdpa.c
> > +++ b/drivers/virtio/virtio_vdpa.c
> > @@ -183,6 +183,8 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
> >                 goto error_new_virtqueue;
> >         }
> >
> > +       vq->num_max = max_num;
> > +
> >         /* Setup virtqueue callback */
> >         cb.callback = callback ? virtio_vdpa_virtqueue_cb : NULL;
> >         cb.private = info;
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index d8fdf170637c..a82620032e43 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -31,6 +31,7 @@ struct virtqueue {
> >         struct virtio_device *vdev;
> >         unsigned int index;
> >         unsigned int num_free;
> > +       unsigned int num_max;
>
> A question, since we export virtqueue to drivers, this means they can
> access vq->num_max directly.
>
> So we probably don't need a helper here.

I think you are right.

Thanks.

>
> Thanks
>
> >         void *priv;
> >  };
> >
> > @@ -80,6 +81,7 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
> >
> >  void *virtqueue_detach_unused_buf(struct virtqueue *vq);
> >
> > +unsigned int virtqueue_get_vring_max_size(struct virtqueue *vq);
> >  unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
> >
> >  bool virtqueue_is_broken(struct virtqueue *vq);
> > --
> > 2.31.0
> >
>
diff mbox series

Patch

diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index 82ff3785bf69..e719af8bdf56 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -958,6 +958,7 @@  static struct virtqueue *vu_setup_vq(struct virtio_device *vdev,
 		goto error_create;
 	}
 	vq->priv = info;
+	vq->num_max = num;
 	num = virtqueue_get_vring_size(vq);
 
 	if (vu_dev->protocol_features &
diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
index 38800e86ed8a..1ae3c56b66b0 100644
--- a/drivers/platform/mellanox/mlxbf-tmfifo.c
+++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
@@ -959,6 +959,8 @@  static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
 			goto error;
 		}
 
+		vq->num_max = vring->num;
+
 		vqs[i] = vq;
 		vring->vq = vq;
 		vq->priv = vring;
diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
index d43d74733f0a..0f7706e23eb9 100644
--- a/drivers/remoteproc/remoteproc_virtio.c
+++ b/drivers/remoteproc/remoteproc_virtio.c
@@ -125,6 +125,8 @@  static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
 		return ERR_PTR(-ENOMEM);
 	}
 
+	vq->num_max = num;
+
 	rvring->vq = vq;
 	vq->priv = rvring;
 
diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index 161d3b141f0d..6b86d0280d6b 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -530,6 +530,9 @@  static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
 		err = -ENOMEM;
 		goto out_err;
 	}
+
+	vq->num_max = info->num;
+
 	/* it may have been reduced */
 	info->num = virtqueue_get_vring_size(vq);
 
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 083ff1eb743d..a20d5a6b5819 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -403,6 +403,8 @@  static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in
 		goto error_new_virtqueue;
 	}
 
+	vq->num_max = num;
+
 	/* Activate the queue */
 	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
 	if (vm_dev->version == 1) {
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index a5e5721145c7..2257f1b3d8ae 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -135,6 +135,8 @@  static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	if (!vq)
 		return ERR_PTR(-ENOMEM);
 
+	vq->num_max = num;
+
 	q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
 	if (q_pfn >> 32) {
 		dev_err(&vp_dev->pci_dev->dev,
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 623906b4996c..e7e0b8c850f6 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -218,6 +218,8 @@  static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	if (!vq)
 		return ERR_PTR(-ENOMEM);
 
+	vq->num_max = num;
+
 	/* activate the queue */
 	vp_modern_set_queue_size(mdev, index, virtqueue_get_vring_size(vq));
 	vp_modern_queue_address(mdev, index, virtqueue_get_desc_addr(vq),
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a5ec724c01d8..4cac600856ad 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2385,6 +2385,20 @@  void vring_transport_features(struct virtio_device *vdev)
 }
 EXPORT_SYMBOL_GPL(vring_transport_features);
 
+/**
+ * virtqueue_get_vring_max_size - return the max size of the virtqueue's vring
+ * @_vq: the struct virtqueue containing the vring of interest.
+ *
+ * Returns the max size of the vring.
+ *
+ * Unlike other operations, this need not be serialized.
+ */
+unsigned int virtqueue_get_vring_max_size(struct virtqueue *_vq)
+{
+	return _vq->num_max;
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_vring_max_size);
+
 /**
  * virtqueue_get_vring_size - return the size of the virtqueue's vring
  * @_vq: the struct virtqueue containing the vring of interest.
diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
index c40f7deb6b5a..9670cc79371d 100644
--- a/drivers/virtio/virtio_vdpa.c
+++ b/drivers/virtio/virtio_vdpa.c
@@ -183,6 +183,8 @@  virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
 		goto error_new_virtqueue;
 	}
 
+	vq->num_max = max_num;
+
 	/* Setup virtqueue callback */
 	cb.callback = callback ? virtio_vdpa_virtqueue_cb : NULL;
 	cb.private = info;
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d8fdf170637c..a82620032e43 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -31,6 +31,7 @@  struct virtqueue {
 	struct virtio_device *vdev;
 	unsigned int index;
 	unsigned int num_free;
+	unsigned int num_max;
 	void *priv;
 };
 
@@ -80,6 +81,7 @@  bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
 
 void *virtqueue_detach_unused_buf(struct virtqueue *vq);
 
+unsigned int virtqueue_get_vring_max_size(struct virtqueue *vq);
 unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
 
 bool virtqueue_is_broken(struct virtqueue *vq);