[dpdk-stable] [Suspected-Phishing][PATCH] net/vhost: fix redundant queue state event

[Maxime Coquelin]

On 6/26/19 8:37 AM, Noa Ezra wrote:
> Hi,
> 
>> -----Original Message-----
>> From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com]
>> Sent: Tuesday, June 25, 2019 11:24 AM
>> To: Noa Ezra <noae at mellanox.com>
>> Cc: Matan Azrad <matan at mellanox.com>; dev at dpdk.org; stable at dpdk.org
>> Subject: Re: [Suspected-Phishing][PATCH] net/vhost: fix redundant queue
>> state event
>>
>>
>>
>> On 6/25/19 9:04 AM, Noa Ezra wrote:
>>> Hi,
>>> What do you think about this patch?
>>>
>>> Thanks,
>>> Noa.
>>>
>>>> -----Original Message-----
>>>> From: Noa Ezra [mailto:noae at mellanox.com]
>>>> Sent: Wednesday, June 19, 2019 9:16 AM
>>>> To: maxime.coquelin at redhat.com
>>>> Cc: Matan Azrad <matan at mellanox.com>; dev at dpdk.org; Noa Ezra
>>>> <noae at mellanox.com>; stable at dpdk.org
>>>> Subject: [Suspected-Phishing][PATCH] net/vhost: fix redundant queue
>>>> state event
>>>>
>>>> In some situations, when a virtual machine is starting,
>>>> vring_state_changed can be called while there was no change in the
>>>> queue state. This fix makes sure that there was really a change in
>>>> the queue state before calling the callback for EVENT_QUEUE_STATE.
>>>>
>>>> Fixes: ee584e9710b9 ("vhost: add driver on top of the library")
>>>> Cc: stable at dpdk.org
>>>> Reviewed-by: Matan Azrad <matan at mellanox.com>
>>>> ---
>>>>    drivers/net/vhost/rte_eth_vhost.c | 4 ++++
>>>>    1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/net/vhost/rte_eth_vhost.c
>>>> b/drivers/net/vhost/rte_eth_vhost.c
>>>> index cad1e5c..fbe7a37 100644
>>>> --- a/drivers/net/vhost/rte_eth_vhost.c
>>>> +++ b/drivers/net/vhost/rte_eth_vhost.c
>>>> @@ -855,6 +855,10 @@ struct vhost_xstats_name_off {
>>>>    	/* won't be NULL */
>>>>    	state = vring_states[eth_dev->data->port_id];
>>>>    	rte_spinlock_lock(&state->lock);
>>>> +	if (state->cur[vring] == enable) {
>>>> +		rte_spinlock_unlock(&state->lock);
>>>> +		return 0;
>>>> +	}
>>>>
>>>>    	state->cur[vring] = enable;
>>>>    	state->max_vring = RTE_MAX(vring, state->max_vring);
>>
>> Maybe the application would want to be notified a new queue is available,
>> even if it is disabled?
> 
> Can you please look again? As I understand it, "enable" is the "new state" parameter (can be enable/disable).
> In this fix I make sure that there was really a change in the state before calling EVENT_QUEUE_STATE (with no change in the state).

Ok, I get it.

Maybe we would want to update state->max_vring even if we don't sent the
event?

Thanks,
Maxime
>>
>>>> --
>>>> 1.8.3.1
>>>