Re: [PATCH] vhost: add vDPA resource cleanup callback

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

Hi Xueming,

On 11/3/21 14:49, Maxime Coquelin wrote:
> 
> 
> On 11/3/21 14:45, Xueming(Steven) Li wrote:
>> On Wed, 2021-11-03 at 09:46 +0100, Maxime Coquelin wrote:
>>>
>>> On 11/3/21 09:41, Xia, Chenbo wrote:
>>>> Hi Xueming,
>>>>
>>>>> -----Original Message-----
>>>>> From: Xueming(Steven) Li <xuemingl@nvidia.com>
>>>>> Sent: Thursday, October 21, 2021 8:36 PM
>>>>> To: maxime.coquelin@redhat.com; dev@dpdk.org
>>>>> Cc: Xia, Chenbo <chenbo.xia@intel.com>
>>>>> Subject: Re: [PATCH] vhost: add vDPA resource cleanup callback
>>>>>
>>>>> On Thu, 2021-10-21 at 14:00 +0200, Maxime Coquelin wrote:
>>>>>> Hi Xueming,
>>>>>>
>>>>>> On 10/19/21 13:39, Xueming Li wrote:
>>>>>>> This patch adds vDPA device cleanup callback to release resources on
>>>>>>> vhost user connection close.
>>>>>>>
>>>>>>> Signed-off-by: Xueming Li <xuemingl@nvidia.com>
>>>>>>> ---
>>>>>>>     lib/vhost/rte_vdpa_dev.h | 3 +++
>>>>>>>     lib/vhost/vhost_user.c   | 6 ++++++
>>>>>>>     2 files changed, 9 insertions(+)
>>>>>>>
>>>>>>> diff --git a/lib/vhost/rte_vdpa_dev.h b/lib/vhost/rte_vdpa_dev.h
>>>>>>> index b0f494815fa..2711004fe05 100644
>>>>>>> --- a/lib/vhost/rte_vdpa_dev.h
>>>>>>> +++ b/lib/vhost/rte_vdpa_dev.h
>>>>>>> @@ -32,6 +32,9 @@ struct rte_vdpa_dev_ops {
>>>>>>>         /** Driver close the device (Mandatory) */
>>>>>>>         int (*dev_close)(int vid);
>>>>>>>
>>>>>>> +    /** Connection closed, clean up resources */
>>>>>>> +    int (*dev_cleanup)(int vid);
>>>>>>> +
>>>>>>>         /** Enable/disable this vring (Mandatory) */
>>>>>>>         int (*set_vring_state)(int vid, int vring, int state);
>>>>>>>
>>>>>>> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
>>>>>>> index 5a894ca0cc7..032b621c86c 100644
>>>>>>> --- a/lib/vhost/vhost_user.c
>>>>>>> +++ b/lib/vhost/vhost_user.c
>>>>>>> @@ -162,6 +162,12 @@ free_mem_region(struct virtio_net *dev)
>>>>>>>     void
>>>>>>>     vhost_backend_cleanup(struct virtio_net *dev)
>>>>>>>     {
>>>>>>> +    struct rte_vdpa_device *vdpa_dev;
>>>>>>> +
>>>>>>> +    vdpa_dev = dev->vdpa_dev;
>>>>>>> +    if (vdpa_dev && vdpa_dev->ops->dev_cleanup != NULL)
>>>>>>> +        vdpa_dev->ops->dev_cleanup(dev->vid);
>>>>>>> +
>>>>>>>         if (dev->mem) {
>>>>>>>             free_mem_region(dev);
>>>>>>>             rte_free(dev->mem);
>>>>>>>
>>>>>>
>>>>>> What will be done there that cannot be done in .dev_close()?
>>>>>
>>>>> .dev_close() mainly handles VM suspend and driver reset. If release
>>>>> everything inside dev_close(), the suspend and resume takes longer 
>>>>> time
>>>>> if number of VQs are huge. Customer want to upgrade VM configuration
>>>>> using suspend and resume, pause customer VM too long can't be 
>>>>> accepted.
>>>>
>>>> By saying 'upgrade VM configuration', do you mean VM memory hotplug? 
>>>> Or something
>>>> more?
>>>>
>>>> Is this patch a next-step improvement of this commit?
>>>>
>>>> commit 127f9c6f7b78a47b73b3e1c39e021cc81a30b4c9
>>>> Author: Matan Azrad <matan@mellanox.com>
>>>> Date:   Mon Jun 29 14:08:19 2020 +0000
>>>>
>>>>       vhost: handle memory hotplug with vDPA devices
>>>>
>>>>       Some vDPA drivers' basic configurations should be updated when 
>>>> the
>>>>       guest memory is hotplugged.
>>>>
>>>>       Close vDPA device before hotplug operation and recreate it 
>>>> after the
>>>>       hotplug operation is done.
>>>>
>>>>       Signed-off-by: Matan Azrad <matan@mellanox.com>
>>>>       Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>>       Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
>>>>
>>>>> So the idea is to cache and reuse resource between dev_close() and
>>>>> dev_conf(). Actually, the two functions looks more like dev_stop() and
>>>>> dev_start().
>>>>>
>>>>> dev_cleanup hooks to vhost backend cleanup which called when socket
>>>>> closed for both client and server mode, a safe point to cleanup all
>>>>> cached resources.
>>>>>
>>>>>> Having the mlx5 implementation of this callback alongside this 
>>>>>> patch may
>>>>>> help to understand.
>>>>>
>>>>> The mlx5 implementation still a prototype, pending on internal review.
>>>>> So I just post the vhost part to get suggestion/comment. Let me 
>>>>> know if
>>>>> the ugly code does help :)
>>>>
>>>> I would prefer to see the mlx implementation with this patch in the 
>>>> same
>>>> patchset to understand the problem. A new callback is fine if the 
>>>> problem
>>>> itself makes sense :)
>>>
>>> FYI, I'm about to apply a patch that marks the vDPA driver API as
>>> internal, when you will submit a new version please apply on top of it.
>>
>> Haven't check your patch yet, but sounds good form subject :)
> 
> The branch is now ready, you can rebase your patch on top of it:
> git://dpdk.org/next/dpdk-next-virtio main

Could you please rebase your patch if you want it in v22.03?

Thanks!
Maxime

> Maxime
> 
>>>
>>> Thanks,
>>> Maxime
>>>
>>>> Thanks,
>>>> Chenbo
>>>>
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>> Maxime
>>>>>>
>>>>
>>>
>>