linux-kernel - Re: [PATCH v1 0/2] vduse: add support for networking devices

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Message-ID: <8128857f-e292-2e41-cdb9-9c5d4a2f79c7@redhat.com>
Date:   Tue, 4 Jul 2023 15:17:22 +0200
From:   Maxime Coquelin <maxime.coquelin@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>, xieyongji@...edance.com,
        david.marchand@...hat.com, lulu@...hat.com,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        xuanzhuo@...ux.alibaba.com, eperezma@...hat.com
Subject: Re: [PATCH v1 0/2] vduse: add support for networking devices



On 7/4/23 11:59, Michael S. Tsirkin wrote:
> On Tue, Jul 04, 2023 at 10:43:07AM +0200, Maxime Coquelin wrote:
>>
>>
>> On 7/3/23 23:45, Michael S. Tsirkin wrote:
>>> On Mon, Jul 03, 2023 at 09:43:49AM +0200, Maxime Coquelin wrote:
>>>>
>>>> On 7/3/23 08:44, Jason Wang wrote:
>>>>> On Sun, Jul 2, 2023 at 9:37 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>>>>>>
>>>>>> On Tue, Jun 27, 2023 at 01:36:50PM +0200, Maxime Coquelin wrote:
>>>>>>> This small series enables virtio-net device type in VDUSE.
>>>>>>> With it, basic operation have been tested, both with
>>>>>>> virtio-vdpa and vhost-vdpa using DPDK Vhost library series
>>>>>>> adding VDUSE support using split rings layout (merged in
>>>>>>> DPDK v23.07-rc1).
>>>>>>>
>>>>>>> Control queue support (and so multiqueue) has also been
>>>>>>> tested, but requires a Kernel series from Jason Wang
>>>>>>> relaxing control queue polling [1] to function reliably.
>>>>>>>
>>>>>>> [1]: https://lore.kernel.org/lkml/CACGkMEtgrxN3PPwsDo4oOsnsSLJfEmBEZ0WvjGRr3whU+QasUg@mail.gmail.com/T/
>>>>>>
>>>>>> Jason promised to post a new version of that patch.
>>>>>> Right Jason?
>>>>>
>>>>> Yes.
>>>>>
>>>>>> For now let's make sure CVQ feature flag is off?
>>>>>
>>>>> We can do that and relax on top of my patch.
>>>>
>>>> I agree? Do you prefer a features negotiation, or failing init (like
>>>> done for VERSION_1) if the VDUSE application advertises CVQ?
>>>>
>>>> Thanks,
>>>> Maxime
>>>
>>> Unfortunately guests fail probe if feature set is inconsistent.
>>> So I don't think passing through features is a good idea,
>>> you need a list of legal bits. And when doing this,
>>> clear CVQ and everything that depends on it.
>>
>> Since this is temporary, while cvq is made more robust, I think it is
>> better to fail VDUSE device creation if CVQ feature is advertised by the
>> VDUSE application, instead of ensuring features depending on CVQ are
>> also cleared.
>>
>> Jason seems to think likewise, would that work for you?
>>
>> Thanks,
>> Maxime
> 
> Nothing is more permanent than temporary solutions.
> My concern would be that hardware devices then start masking CVQ
> intentionally just to avoid the pain of broken software.

Got it, I'll add a patch on top that filters out CVQ feature and all the
features that depend on it.

Thanks,
Maxime

> 
>>>
>>>
>>>>> Thanks
>>>>>
>>>>>>
>>>>>>> RFC -> v1 changes:
>>>>>>> ==================
>>>>>>> - Fail device init if it does not support VERSION_1 (Jason)
>>>>>>>
>>>>>>> Maxime Coquelin (2):
>>>>>>>      vduse: validate block features only with block devices
>>>>>>>      vduse: enable Virtio-net device type
>>>>>>>
>>>>>>>     drivers/vdpa/vdpa_user/vduse_dev.c | 15 +++++++++++----
>>>>>>>     1 file changed, 11 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> --
>>>>>>> 2.41.0
>>>>>>
>>>>>
>>>
>