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

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Message-ID: <560bcbe5-f0db-ed61-8ec0-043031145fe4@redhat.com>
Date:   Tue, 26 Apr 2022 11:45:15 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, sgarzare@...hat.com,
        eperezma@...hat.com, lulu@...hat.com, tglx@...utronix.de,
        peterz@...radead.org, paulmck@...nel.org, maz@...nel.org,
        pasic@...ux.ibm.com
Subject: Re: [PATCH V3 7/9] virtio: allow to unbreak virtqueue


在 2022/4/25 22:04, Michael S. Tsirkin 写道:
> On Mon, Apr 25, 2022 at 02:44:06PM +0200, Cornelia Huck wrote:
>> On Mon, Apr 25 2022, Jason Wang <jasowang@...hat.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@...hat.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


Ok, so I think then we don't want it to be exported.


> with a bit comment explaining it's only safe to call during probe.


Will do.

Thanks


>