Re: Re: Re: Re: [PATCH v2 1/2] virtio: abstract virtqueue related methods

zhenwei pi
2023-05-18T11:04:17Z

On 5/18/23 18:09, Michael S. Tsirkin wrote:
> On Thu, May 18, 2023 at 08:47:22AM +0800, zhenwei pi wrote:
>> On 5/17/23 18:39, Michael S. Tsirkin wrote:
>>> On Wed, May 17, 2023 at 04:35:55PM +0800, zhenwei pi wrote:
>>>>
>>>>
>>>> On 5/17/23 15:46, Christoph Hellwig wrote:
>>>>> On Wed, May 17, 2023 at 03:43:03PM +0800, zhenwei pi wrote:
>>>>>> I have a plan to introduce 'Virtio Over Fabrics'(TCP&RDMA) as Virtio
>>>>>> transport, as mentioned in cover letter of this series:
>>>>>> 3 weeks ago, I posted a proposal 'Virtio Over Fabrics':
>>>>>> https://lists.oasis-open.org/archives/virtio-comment/202304/msg00442.html
>>>>>
>>>>> Just don't do it. Please define your own protocols over RDMA or TCP
>>>>> for exactly the operations you need (for many they will already exist)
>>>>> instead of piggyg backing on virtio and making everyone else pay the
>>>>> price.
>>>>>
>>>>
>>>> Hi
>>>>
>>>> 1, `virtqueue_add_inbuf` in current version:
>>>> static inline int virtqueue_add_inbuf(struct virtqueue *vq,
>>>> struct scatterlist *sg,
>>>> unsigned int num,
>>>> void *data,
>>>> gfp_t gfp)
>>>> {
>>>> if (likely(!vq->abstract))
>>>> return vring_virtqueue_add_sgs(vq, &sg, num, 0, 1, data,
>>>> NULL, gfp);
>>>>
>>>> return vq->add_sgs(vq, &sg, num, 0, 1, data, NULL, gfp);
>>>> }
>>>>
>>>> And disassemble 'virtinput_queue_evtbuf':
>>>> static void virtinput_queue_evtbuf(struct virtio_input *vi,
>>>> struct virtio_input_event *evtbuf)
>>>> {
>>>> struct scatterlist sg[1];
>>>>
>>>> sg_init_one(sg, evtbuf, sizeof(*evtbuf));
>>>> virtqueue_add_inbuf(vi->evt, sg, 1, evtbuf, GFP_ATOMIC);
>>>> }
>>>>
>>>> I notice that two instructions are newly added for vring like:
>>>> 24d: 80 78 35 00 cmpb $0x0,0x35(%rax)
>>>> 251: 75 3f jne 292
>>>>
>>>> Is it an expensive price...
>>>
>>> Can we somehow only override the kick method?
>>> Then take the ring and send it over ...
>>>
>>
>> Could you please take a look at this code?
>> https://github.com/pizhenwei/linux/blob/virtio-of-github/drivers/virtio/virtio_fabrics.c#LL861C13-L861C23
>
> what am I looking at here?
>
> Looks like at least vof_handle_vq duplicates some code from vringh.
> But besides that yes, that's the idea.
>

OK, I'd drop this series.

Cc Jason & Stefan.

--
zhenwei pi