Re: [PATCH V3 7/9] virtio: allow to unbreak virtqueue

Michael S. Tsirkin
2022-04-25T14:05:17Z

On Mon, Apr 25, 2022 at 02:44:06PM +0200, Cornelia Huck wrote:
> On Mon, Apr 25 2022, Jason Wang <jasowang@redhat.com> wrote:
>
> > This patch allows the virtio_break_device() to accept a boolean value
> > then we can unbreak the virtqueue.
> >
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> > drivers/char/virtio_console.c | 2 +-
> > drivers/crypto/virtio/virtio_crypto_core.c | 2 +-
> > drivers/s390/virtio/virtio_ccw.c | 4 ++--
> > drivers/virtio/virtio_pci_common.c | 2 +-
> > drivers/virtio/virtio_ring.c | 4 ++--
> > include/linux/virtio.h | 2 +-
> > 6 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > index e3c430539a17..afede977f7b3 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1958,7 +1958,7 @@ static void virtcons_remove(struct virtio_device *vdev)
> > spin_unlock_irq(&pdrvdata_lock);
> >
> > /* Device is going away, exit any polling for buffers */
> > - virtio_break_device(vdev);
> > + virtio_break_device(vdev, true);
> > if (use_multiport(portdev))
> > flush_work(&portdev->control_work);
> > else
> > diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
> > index c6f482db0bc0..fd17f3f2e958 100644
> > --- a/drivers/crypto/virtio/virtio_crypto_core.c
> > +++ b/drivers/crypto/virtio/virtio_crypto_core.c
> > @@ -215,7 +215,7 @@ static int virtcrypto_update_status(struct virtio_crypto *vcrypto)
> > dev_warn(&vcrypto->vdev->dev,
> > "Unknown status bits: 0x%x\n", status);
> >
> > - virtio_break_device(vcrypto->vdev);
> > + virtio_break_device(vcrypto->vdev, true);
> > return -EPERM;
> > }
> >
> > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> > index c19f07a82d62..9a963f5af5b5 100644
> > --- a/drivers/s390/virtio/virtio_ccw.c
> > +++ b/drivers/s390/virtio/virtio_ccw.c
> > @@ -1211,7 +1211,7 @@ static void virtio_ccw_remove(struct ccw_device *cdev)
> >
> > if (vcdev && cdev->online) {
> > if (vcdev->device_lost)
> > - virtio_break_device(&vcdev->vdev);
> > + virtio_break_device(&vcdev->vdev, true);
> > unregister_virtio_device(&vcdev->vdev);
> > spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
> > dev_set_drvdata(&cdev->dev, NULL);
> > @@ -1228,7 +1228,7 @@ static int virtio_ccw_offline(struct ccw_device *cdev)
> > if (!vcdev)
> > return 0;
> > if (vcdev->device_lost)
> > - virtio_break_device(&vcdev->vdev);
> > + virtio_break_device(&vcdev->vdev, true);
> > unregister_virtio_device(&vcdev->vdev);
> > spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
> > dev_set_drvdata(&cdev->dev, NULL);
> > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> > index d724f676608b..39a711ddff30 100644
> > --- a/drivers/virtio/virtio_pci_common.c
> > +++ b/drivers/virtio/virtio_pci_common.c
> > @@ -583,7 +583,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
> > * layers can abort any ongoing operation.
> > */
> > if (!pci_device_is_present(pci_dev))
> > - virtio_break_device(&vp_dev->vdev);
> > + virtio_break_device(&vp_dev->vdev, true);
> >
> > pci_disable_sriov(pci_dev);
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index cfb028ca238e..6da13495a70c 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2382,7 +2382,7 @@ EXPORT_SYMBOL_GPL(virtqueue_is_broken);
> > * This should prevent the device from being used, allowing drivers to
> > * recover. You may need to grab appropriate locks to flush.
> > */
> > -void virtio_break_device(struct virtio_device *dev)
> > +void virtio_break_device(struct virtio_device *dev, bool broken)
>
> I think we need to be careful to say when it is safe to unset 'broken'.
>
> The current callers set all queues to broken in case of surprise removal
> (ccw, pci), removal (console), or the device behaving badly
> (crypto). There's also code setting individual queues to broken. We do
> not want to undo any of these, unless the device has gone through a
> reset in the meanwhile. Maybe add:
>
> "It is only safe to call this function to *remove* the broken flag for a
> device that is (re)transitioning to becoming usable; calling it that way
> during normal usage may have unpredictable consequences."
>
> (Not sure how to word this; especially if we consider future usage of
> queue reset.)

Right. I would prefer __virtio_unbreak_device or something similar
with a bit comment explaining it's only safe to call during probe.

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MST