Re: [dpdk-dev] [PATCH v1 1/4] vhost: support host notifier queue configuration

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 6/19/20 3:28 PM, Matan Azrad wrote:
> 
> 
> From: Maxime Coquelin:
>> On 6/18/20 6:28 PM, Matan Azrad wrote:
>>> As an arrangement to per queue operations in the vDPA device it is
>>> needed to change the next experimental API:
>>>
>>> The API ``rte_vhost_host_notifier_ctrl`` was changed to be per queue
>>> instead of per device.
>>>
>>> A `qid` parameter was added to the API arguments list.
>>>
>>> Setting the parameter to the value VHOST_QUEUE_ALL will configure the
>>> host notifier to all the device queues as done before this patch.
>>>
>>> Signed-off-by: Matan Azrad <matan@mellanox.com>
>>> ---
>>>  doc/guides/rel_notes/release_20_08.rst |  2 ++
>>>  drivers/vdpa/ifc/ifcvf_vdpa.c          |  6 +++---
>>>  drivers/vdpa/mlx5/mlx5_vdpa.c          |  5 +++--
>>>  lib/librte_vhost/rte_vdpa.h            |  8 ++++++--
>>>  lib/librte_vhost/rte_vhost.h           |  2 ++
>>>  lib/librte_vhost/vhost.h               |  3 ---
>>>  lib/librte_vhost/vhost_user.c          | 18 ++++++++++++++----
>>>  7 files changed, 30 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/doc/guides/rel_notes/release_20_08.rst
>>> b/doc/guides/rel_notes/release_20_08.rst
>>> index ba16d3b..9732959 100644
>>> --- a/doc/guides/rel_notes/release_20_08.rst
>>> +++ b/doc/guides/rel_notes/release_20_08.rst
>>> @@ -111,6 +111,8 @@ API Changes
>>>     Also, make sure to start the actual text at the margin.
>>>
>> =========================================================
>>>
>>> +* vhost: The API of ``rte_vhost_host_notifier_ctrl`` was changed to
>>> +be per
>>> +  queue and not per device, a qid parameter was added to the arguments
>> list.
>>>
>>>  ABI Changes
>>>  -----------
>>> diff --git a/drivers/vdpa/ifc/ifcvf_vdpa.c
>>> b/drivers/vdpa/ifc/ifcvf_vdpa.c index ec97178..336837a 100644
>>> --- a/drivers/vdpa/ifc/ifcvf_vdpa.c
>>> +++ b/drivers/vdpa/ifc/ifcvf_vdpa.c
>>> @@ -839,7 +839,7 @@ struct internal_list {
>>>  	vdpa_ifcvf_stop(internal);
>>>  	vdpa_disable_vfio_intr(internal);
>>>
>>> -	ret = rte_vhost_host_notifier_ctrl(vid, false);
>>> +	ret = rte_vhost_host_notifier_ctrl(vid, VHOST_QUEUE_ALL, false);
>>>  	if (ret && ret != -ENOTSUP)
>>>  		goto error;
>>>
>>> @@ -858,7 +858,7 @@ struct internal_list {
>>>  	if (ret)
>>>  		goto stop_vf;
>>>
>>> -	rte_vhost_host_notifier_ctrl(vid, true);
>>> +	rte_vhost_host_notifier_ctrl(vid, VHOST_QUEUE_ALL, true);
>>>
>>>  	internal->sw_fallback_running = true;
>>>
>>> @@ -893,7 +893,7 @@ struct internal_list {
>>>  	rte_atomic32_set(&internal->dev_attached, 1);
>>>  	update_datapath(internal);
>>>
>>> -	if (rte_vhost_host_notifier_ctrl(vid, true) != 0)
>>> +	if (rte_vhost_host_notifier_ctrl(vid, VHOST_QUEUE_ALL, true) != 0)
>>>  		DRV_LOG(NOTICE, "vDPA (%d): software relay is used.", did);
>>>
>>>  	return 0;
>>> diff --git a/drivers/vdpa/mlx5/mlx5_vdpa.c
>>> b/drivers/vdpa/mlx5/mlx5_vdpa.c index 9e758b6..8ea1300 100644
>>> --- a/drivers/vdpa/mlx5/mlx5_vdpa.c
>>> +++ b/drivers/vdpa/mlx5/mlx5_vdpa.c
>>> @@ -147,7 +147,8 @@
>>>  	int ret;
>>>
>>>  	if (priv->direct_notifier) {
>>> -		ret = rte_vhost_host_notifier_ctrl(priv->vid, false);
>>> +		ret = rte_vhost_host_notifier_ctrl(priv->vid,
>> VHOST_QUEUE_ALL,
>>> +						   false);
>>>  		if (ret != 0) {
>>>  			DRV_LOG(INFO, "Direct HW notifier FD cannot be "
>>>  				"destroyed for device %d: %d.", priv->vid,
>> ret); @@ -155,7 +156,7
>>> @@
>>>  		}
>>>  		priv->direct_notifier = 0;
>>>  	}
>>> -	ret = rte_vhost_host_notifier_ctrl(priv->vid, true);
>>> +	ret = rte_vhost_host_notifier_ctrl(priv->vid, VHOST_QUEUE_ALL,
>>> +true);
>>>  	if (ret != 0)
>>>  		DRV_LOG(INFO, "Direct HW notifier FD cannot be configured
>> for"
>>>  			" device %d: %d.", priv->vid, ret); diff --git
>>> a/lib/librte_vhost/rte_vdpa.h b/lib/librte_vhost/rte_vdpa.h index
>>> ecb3d91..2db536c 100644
>>> --- a/lib/librte_vhost/rte_vdpa.h
>>> +++ b/lib/librte_vhost/rte_vdpa.h
>>> @@ -202,22 +202,26 @@ struct rte_vdpa_device *  int
>>> rte_vdpa_get_device_num(void);
>>>
>>> +#define VHOST_QUEUE_ALL VHOST_MAX_VRING
>>> +
>>>  /**
>>>   * @warning
>>>   * @b EXPERIMENTAL: this API may change without prior notice
>>>   *
>>> - * Enable/Disable host notifier mapping for a vdpa port.
>>> + * Enable/Disable host notifier mapping for a vdpa queue.
>>>   *
>>>   * @param vid
>>>   *  vhost device id
>>>   * @param enable
>>>   *  true for host notifier map, false for host notifier unmap
>>> + * @param qid
>>> + *  vhost queue id, VHOST_QUEUE_ALL to configure all the device
>>> + queues
>> I would prefer two APIs that passing a special ID that means all queues:
>>
>> rte_vhost_host_notifier_ctrl(int vid, uint16_t qid, bool enable);
>> rte_vhost_host_notifier_ctrl_all(int vid, bool enable);
>>
>> I think it is clearer for the user of the API.
>> Or if you think an extra API is overkill, just let the driver loop on all the
>> queues.
> 
> We have a lot of options here with pros and cons.
> I took the rte_eth_dev_callback_register style.

Ok, I didn't looked at this code.

> It is less intrusive with minimum code change.  
> 
> I'm not sure what is the clearest option but the current suggestion is well defined and 
> allows to configure all the queues too.
> 
> Let me know what you prefer....

I personally don't like the style, but I can live with it if you prefer
doing it like that.

If you do it that way, you will have to rename VHOST_QUEUE_ALL to
RTE_VHOST_QUEUE_ALL, VHOST_MAX_VRING  to RTE_VHOST_MAX_VRING and
VHOST_MAX_QUEUE_PAIRS to RTE_VHOST_MAX_QUEUE_PAIRS as it will become
part of the ABI.

Not that it also means that we won't be able to increase the maximum
number of rings without breaking the ABI.

>>>   * @return
>>>   *  0 on success, -1 on failure
>>>   */
>>>  __rte_experimental
>>>  int
>>> -rte_vhost_host_notifier_ctrl(int vid, bool enable);
>>> +rte_vhost_host_notifier_ctrl(int vid, uint16_t qid, bool enable);
>>>
>>>  /**
>