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Subject: Re: [PATCH V2 4/4] virtio/vdpa: clear the virtqueue state during
 probe
To:     Eli Cohen <elic@nvidia.com>
Cc:     mst@redhat.com, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        netdev@vger.kernel.org, eli@mellanox.com
References: <20210602021043.39201-1-jasowang@redhat.com>
 <20210602021043.39201-5-jasowang@redhat.com>
 <20210602061723.GB8662@mtl-vdi-166.wap.labs.mlnx>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <7ce52bd6-60b7-b733-9881-682cfba51ad8@redhat.com>
Date:   Wed, 2 Jun 2021 15:07:00 +0800
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?? 2021/6/2 ????2:17, Eli Cohen д??:
> On Wed, Jun 02, 2021 at 10:10:43AM +0800, Jason Wang wrote:
>> From: Eli Cohen <elic@nvidia.com>
>>
>> Clear the available index as part of the initialization process to
>> clear and values that might be left from previous usage of the device.
>> For example, if the device was previously used by vhost_vdpa and now
>> probed by vhost_vdpa, you want to start with indices.
>>
>> Fixes: c043b4a8cf3b ("virtio: introduce a vDPA based transport")
>> Signed-off-by: Eli Cohen <elic@nvidia.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   drivers/virtio/virtio_vdpa.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
>> index e28acf482e0c..e1a141135992 100644
>> --- a/drivers/virtio/virtio_vdpa.c
>> +++ b/drivers/virtio/virtio_vdpa.c
>> @@ -142,6 +142,8 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
>>   	struct vdpa_callback cb;
>>   	struct virtqueue *vq;
>>   	u64 desc_addr, driver_addr, device_addr;
>> +	/* Assume split virtqueue, switch to packed if necessary */
>> +	struct vdpa_vq_state state = {0};
>>   	unsigned long flags;
>>   	u32 align, num;
>>   	int err;
>> @@ -191,6 +193,19 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
>>   		goto err_vq;
>>   	}
>>   
>> +	/* reset virtqueue state index */
>> +	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
>> +		struct vdpa_vq_state_packed *s = &state.packed;
>> +
>> +		s->last_avail_counter = 1;
>> +		s->last_avail_idx = 0;
> It's already 0
>
>> +		s->last_used_counter = 1;
>> +		s->last_used_idx = 0;
> already 0


Yes, but for completeness and make code easy to read, it's no harm to 
keep them I think.

Thanks


>
>> +	}
>> +	err = ops->set_vq_state(vdpa, index, &state);
>> +	if (err)
>> +		goto err_vq;
>> +
>>   	ops->set_vq_ready(vdpa, index, 1);
>>   
>>   	vq->priv = info;
>> -- 
>> 2.25.1
>>