Re: [dpdk-dev] [PATCH] vhost: call rte_vhost_enable_guest_notification only on enabled queues

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 4/7/2016 11:29 PM, Loftus, Ciara wrote:
>> On 4/7/2016 8:29 AM, Rich Lane wrote:
>>> If the vhost PMD were configured with more queues than the guest, the
>> old
>>> code would segfault in rte_vhost_enable_guest_notification due to a NULL
>>> virtqueue pointer.
>>>
>>> Fixes: ee584e9710b9 ("vhost: add driver on top of the library")
>>> Signed-off-by: Rich Lane <rich.lane@bigswitch.com>
>>> ---
>>>    drivers/net/vhost/rte_eth_vhost.c | 5 +++--
>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/vhost/rte_eth_vhost.c
>> b/drivers/net/vhost/rte_eth_vhost.c
>>> index b1eb082..310cbef 100644
>>> --- a/drivers/net/vhost/rte_eth_vhost.c
>>> +++ b/drivers/net/vhost/rte_eth_vhost.c
>>> @@ -265,7 +265,6 @@ new_device(struct virtio_net *dev)
>>>    		vq->device = dev;
>>>    		vq->internal = internal;
>>>    		vq->port = eth_dev->data->port_id;
>>> -		rte_vhost_enable_guest_notification(dev, vq-
>>> virtqueue_id, 0);
>>>    	}
>>>    	for (i = 0; i < eth_dev->data->nb_tx_queues; i++) {
>>>    		vq = eth_dev->data->tx_queues[i];
>>> @@ -274,9 +273,11 @@ new_device(struct virtio_net *dev)
>>>    		vq->device = dev;
>>>    		vq->internal = internal;
>>>    		vq->port = eth_dev->data->port_id;
>>> -		rte_vhost_enable_guest_notification(dev, vq-
>>> virtqueue_id, 0);
>>>    	}
>>>
>>> +	for (i = 0; i < dev->virt_qp_nb * VIRTIO_QNUM; i++)
>>> +		rte_vhost_enable_guest_notification(dev, i, 0);
>>> +
>>>    	dev->flags |= VIRTIO_DEV_RUNNING;
>>>    	dev->priv = eth_dev;
>>>    	eth_dev->data->dev_link.link_status = ETH_LINK_UP;
>> Just one question, when qemu starts a vm, usually, only one queue is
>> enabled, then only 1 tx and 1 rx are called
>> rte_vhost_enable_guest_notification; but after system is up, we use
>> "ethtool -K eth0 combined x" to enable multiqueues, there's no chance to
>> call rte_vhost_enable_guest_notification for other queues, right?
> As far as I know, virt_qp_nb will report the number of queues available, regardless of their state enabled/disabled. So for example if we have 4 queues, but only one enabled, virt_qp_nb should still = 4 and rte_vhost_enable_guest_notification() will be called for all of these queues.

Oh, yes. I failed to really get multiqueue configured right, which leads 
to the wrong conclusion. Sorry.

Thanks,
Jianfeng

>
> Thanks,
> Ciara
>
>> Thanks,
>> Jianfeng