linux-kernel - Re: [PATCH V3 18/19] virtio_vdpa: don't warn when fail to disable vq

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Message-ID: <2911e3c2-84ff-006a-24ba-fb6aea9d25d5@redhat.com>
Date:   Mon, 8 Feb 2021 12:15:39 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, shahafs@...lanox.com,
        lulu@...hat.com, sgarzare@...hat.com, rdunlap@...radead.org
Subject: Re: [PATCH V3 18/19] virtio_vdpa: don't warn when fail to disable vq


On 2021/2/5 下午11:24, Michael S. Tsirkin wrote:
> On Mon, Jan 04, 2021 at 02:55:02PM +0800, Jason Wang wrote:
>> There's no guarantee that the device can disable a specific virtqueue
>> through set_vq_ready(). One example is the modern virtio-pci
>> device. So this patch removes the warning.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>
> Do we need the read as a kind of flush though?


The problem is that PCI forbids write 0 to queue_enable. So I'm not sure 
what kind of flush do we need here?

Thanks


>
>> ---
>>   drivers/virtio/virtio_vdpa.c | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
>> index 4a9ddb44b2a7..e28acf482e0c 100644
>> --- a/drivers/virtio/virtio_vdpa.c
>> +++ b/drivers/virtio/virtio_vdpa.c
>> @@ -225,9 +225,8 @@ static void virtio_vdpa_del_vq(struct virtqueue *vq)
>>   	list_del(&info->node);
>>   	spin_unlock_irqrestore(&vd_dev->lock, flags);
>>   
>> -	/* Select and deactivate the queue */
>> +	/* Select and deactivate the queue (best effort) */
>>   	ops->set_vq_ready(vdpa, index, 0);
>> -	WARN_ON(ops->get_vq_ready(vdpa, index));
>>   
>>   	vring_del_virtqueue(vq);
>>   
>> -- 
>> 2.25.1