Date:   Wed, 13 Apr 2022 16:48:04 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v9 23/32] virtio_pci: queue_reset: support VIRTIO_F_RING_RESET

On Tue, 12 Apr 2022 15:07:58 +0800, Jason Wang <jasowang@...hat.com> wrote:
>
> 在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> > This patch implements virtio pci support for QUEUE RESET.
> >
> > Performing reset on a queue is divided into these steps:
> >
> >   1. notify the device to reset the queue
> >   2. recycle the buffer submitted
> >   3. reset the vring (may re-alloc)
> >   4. 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@...ux.alibaba.com>
> > ---
> >   drivers/virtio/virtio_pci_common.c |  8 +--
> >   drivers/virtio/virtio_pci_modern.c | 84 ++++++++++++++++++++++++++++++
> >   drivers/virtio/virtio_ring.c       |  2 +
> >   include/linux/virtio.h             |  1 +
> >   4 files changed, 92 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) {
>
>
> On which condition that we may hit this path?

As discussed in patch 31, it may fail when renable vq.

Thanks.

>
>
> > +		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..cb5d38f1c9c8 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 +202,83 @@ 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;
> > +
> > +	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);
> > +
> > +	/* For the case where vq has an exclusive irq, to prevent the irq from
> > +	 * being received again and the pending irq, call disable_irq().
> > +	 *
> > +	 * In the scenario based on shared interrupts, vq will be searched from
> > +	 * the queue virtqueues. Since the previous list_del() has been deleted
> > +	 * from the queue, it is impossible for vq to be called in this case.
> > +	 * There is no need to close the corresponding interrupt.
> > +	 */
> > +	if (vp_dev->per_vq_vectors && info->msix_vector != VIRTIO_MSI_NO_VECTOR)
> > +		disable_irq(pci_irq_vector(vp_dev->pci_dev, info->msix_vector));
>
>
> See the previous discussion and the revert of the first try to harden
> the interrupt. We probably can't use disable_irq() since it conflicts
> with the affinity managed IRQ that is used by some drivers.
>
> We need to use synchonize_irq() and per virtqueue flag instead. As
> mentioned in previous patches, this could be done on top of my rework on
> the IRQ hardening .
>
>
> > +
> > +	vq->reset = true;
> > +
> > +	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)
> > +		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);
> > +
> > +	if (vp_dev->per_vq_vectors && info->msix_vector != VIRTIO_MSI_NO_VECTOR)
> > +		enable_irq(pci_irq_vector(vp_dev->pci_dev, info->msix_vector));
>
>
> We had the same issue as disable_irq().
>
> Thanks
>
>
> > +
> > +	vq->reset = false;
> > +
> > +	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 +487,8 @@ 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 +507,8 @@ 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 */
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 6250e19fc5bf..91937e21edca 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2028,6 +2028,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
> >   	vq->vq.vdev = vdev;
> >   	vq->vq.name = name;
> >   	vq->vq.index = index;
> > +	vq->vq.reset = false;
> >   	vq->notify = notify;
> >   	vq->weak_barriers = weak_barriers;
> >
> > @@ -2508,6 +2509,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> >   	vq->vq.vdev = vdev;
> >   	vq->vq.name = name;
> >   	vq->vq.index = index;
> > +	vq->vq.reset = false;
> >   	vq->notify = notify;
> >   	vq->weak_barriers = weak_barriers;
> >
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index c86ff02e0ca0..33ab003c5100 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -33,6 +33,7 @@ struct virtqueue {
> >   	unsigned int num_free;
> >   	unsigned int num_max;
> >   	void *priv;
> > +	bool reset;
> >   };
> >
> >   int virtqueue_add_outbuf(struct virtqueue *vq,
>

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