[PATCH v7 17/26] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

[Xuan Zhuo]

On Wed, 9 Mar 2022 16:54:10 +0800, Jason Wang <jasowang at redhat.com> wrote:
>
> 在 2022/3/8 下午8:35, Xuan Zhuo 写道:
> > This patch implements virtio pci support for QUEUE RESET.
> >
> > Performing reset on a queue is divided into these steps:
> >
> >   1. virtio_reset_vq()              - notify the device to reset the queue
> >   2. virtqueue_detach_unused_buf()  - recycle the buffer submitted
> >   3. virtqueue_reset_vring()        - reset the vring (may re-alloc)
> >   4. virtio_enable_resetq()         - mmap vring to device, and enable the queue
> >
> > This patch implements virtio_reset_vq(), virtio_enable_resetq() in the
> > pci scenario.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> > ---
> >   drivers/virtio/virtio_pci_common.c |  8 +--
> >   drivers/virtio/virtio_pci_modern.c | 83 ++++++++++++++++++++++++++++++
> >   2 files changed, 88 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> > index fdbde1db5ec5..863d3a8a0956 100644
> > --- a/drivers/virtio/virtio_pci_common.c
> > +++ b/drivers/virtio/virtio_pci_common.c
> > @@ -248,9 +248,11 @@ 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_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 49a4493732cf..3c67d3607802 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 */
> > @@ -199,6 +202,82 @@ static int vp_active_vq(struct virtqueue *vq, u16 msix_vec)
> >   	return 0;
> >   }
> >
> > +static int vp_modern_reset_vq(struct virtqueue *vq)
> > +{
> > +	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> > +	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> > +	struct virtio_pci_vq_info *info;
> > +	unsigned long flags;
> > +	unsigned int irq;
> > +
> > +	if (!virtio_has_feature(vq->vdev, VIRTIO_F_RING_RESET))
> > +		return -ENOENT;
> > +
> > +	vp_modern_set_queue_reset(mdev, vq->index);
> > +
> > +	info = vp_dev->vqs[vq->index];
> > +
> > +	/* delete vq from irq handler */
> > +	spin_lock_irqsave(&vp_dev->lock, flags);
> > +	list_del(&info->node);
> > +	spin_unlock_irqrestore(&vp_dev->lock, flags);
> > +
> > +	INIT_LIST_HEAD(&info->node);
> > +
> > +	vq->reset = VIRTIO_VQ_RESET_STEP_DEVICE;
> > +
> > +	/* sync irq callback. */
> > +	if (vp_dev->intx_enabled) {
> > +		irq = vp_dev->pci_dev->irq;
> > +
> > +	} else {
> > +		if (info->msix_vector == VIRTIO_MSI_NO_VECTOR)
> > +			return 0;
> > +
> > +		irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
> > +	}
> > +
> > +	synchronize_irq(irq);
>
>
> Synchronize_irq() is not sufficient here since it breaks the effort of
> the interrupt hardening which is done by commits:
>
> 080cd7c3ac87 virtio-pci: harden INTX interrupts
> 9e35276a5344 virtio_pci: harden MSI-X interrupts
>
> Unfortunately  080cd7c3ac87 introduces an issue that disable_irq() were
> used for the affinity managed irq but we're discussing a fix.

I need to understand it first.

>
>
> > +
> > +	return 0;
> > +}
> > +
> > +static int vp_modern_enable_reset_vq(struct virtqueue *vq)
> > +{
> > +	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
> > +	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
> > +	struct virtio_pci_vq_info *info;
> > +	unsigned long flags, index;
> > +	int err;
> > +
> > +	if (vq->reset != VIRTIO_VQ_RESET_STEP_VRING_ATTACH)
> > +		return -EBUSY;
> > +
> > +	index = vq->index;
> > +	info = vp_dev->vqs[index];
> > +
> > +	/* check queue reset status */
> > +	if (vp_modern_get_queue_reset(mdev, index) != 1)
> > +		return -EBUSY;
> > +
> > +	err = vp_active_vq(vq, info->msix_vector);
> > +	if (err)
> > +		return err;
> > +
> > +	if (vq->callback) {
> > +		spin_lock_irqsave(&vp_dev->lock, flags);
> > +		list_add(&info->node, &vp_dev->virtqueues);
> > +		spin_unlock_irqrestore(&vp_dev->lock, flags);
> > +	} else {
> > +		INIT_LIST_HEAD(&info->node);
> > +	}
> > +
> > +	vp_modern_set_queue_enable(&vp_dev->mdev, index, true);
>
>
> Any reason we need to check queue_enable() here?

The purpose of this function is to enable a reset vq, so call queue_enable() to
activate it.

Thanks.

>
> Thanks
>
>
> > +	vq->reset = VIRTIO_VQ_RESET_STEP_NONE;
> > +
> > +	return 0;
> > +}
> > +
> >   static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
> >   {
> >   	return vp_modern_config_vector(&vp_dev->mdev, vector);
> > @@ -407,6 +486,8 @@ 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 = {
> > @@ -425,6 +506,8 @@ 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 */
>