linux-kernel - Re: Re: Re: Re: [PATCH v2 0/2] virtio: abstract virtqueue related methods

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Date:   Wed, 17 May 2023 14:21:09 +0800
From:   zhenwei pi <pizhenwei@...edance.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     stefanha@...hat.com, jasowang@...hat.com,
        xuanzhuo@...ux.alibaba.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: Re: Re: Re: [PATCH v2 0/2] virtio: abstract virtqueue related
 methods

On 5/17/23 14:10, Michael S. Tsirkin wrote:
> On Wed, May 17, 2023 at 12:58:10PM +0800, zhenwei pi wrote:
>> On 5/17/23 11:57, Michael S. Tsirkin wrote:
>>> On Wed, May 17, 2023 at 11:51:03AM +0800, zhenwei pi wrote:
>>>>
>>>>
>>>> On 5/17/23 11:46, Michael S. Tsirkin wrote:
>>>>> On Wed, May 17, 2023 at 10:54:22AM +0800, zhenwei pi wrote:
>>>>>> v1 -> v2:
>>>>>> - Suggested by MST, use fast path for vring based performance
>>>>>> sensitive API.
>>>>>> - Reduce changes in tools/virtio.
>>>>>>
>>>>>> Add test result(no obvious change):
>>>>>> Before:
>>>>>> time ./vringh_test --parallel
>>>>>> Using CPUS 0 and 191
>>>>>> Guest: notified 10036893, pinged 68278
>>>>>> Host: notified 68278, pinged 3093532
>>>>>>
>>>>>> real	0m14.463s
>>>>>> user	0m6.437s
>>>>>> sys	0m8.010s
>>>>>>
>>>>>> After:
>>>>>> time ./vringh_test --parallel
>>>>>> Using CPUS 0 and 191
>>>>>> Guest: notified 10036709, pinged 68347
>>>>>> Host: notified 68347, pinged 3085292
>>>>>>
>>>>>> real	0m14.196s
>>>>>> user	0m6.289s
>>>>>> sys	0m7.885s
>>>>>>
>>>>>> v1:
>>>>>> Hi,
>>>>>>
>>>>>> 3 weeks ago, I posted a proposal 'Virtio Over Fabrics':
>>>>>> https://lists.oasis-open.org/archives/virtio-comment/202304/msg00442.html
>>>>>>
>>>>>> Jason and Stefan pointed out that a non-vring based virtqueue has a
>>>>>> chance to overwrite virtqueue instead of using vring virtqueue.
>>>>>>
>>>>>> Then I try to abstract virtqueue related methods in this series, the
>>>>>> details changes see the comment of patch 'virtio: abstract virtqueue related methods'.
>>>>>>
>>>>>> Something is still remained:
>>>>>> - __virtqueue_break/__virtqueue_unbreak is supposed to use by internal
>>>>>>      virtio core, I'd like to rename them to vring_virtqueue_break
>>>>>>      /vring_virtqueue_unbreak. Is this reasonable?
>>>>>
>>>>> Why? These just set a flag?
>>>>>
>>>>
>>>> Rename '__virtqueue_break' to 'vring_virtqueue_break', to make symbols
>>>> exported from virtio_ring.ko have unified prefix 'vring_virtqueue_xxx'.
>>>
>>> I just do not see why you need these callbacks at all.
>>>
>>
>> I use these callbacks for break/unbreak device like:
>> static inline void virtio_break_device(struct virtio_device *dev)
>> {
>> 	struct virtqueue *vq;
>>
>> 	spin_lock(&dev->vqs_list_lock);
>> 	list_for_each_entry(vq, &dev->vqs, list) {
>> 		vq->__break(vq);
>> 	}
>> 	spin_unlock(&dev->vqs_list_lock);
>> }
> 
> why do this? backend knows they are broken.
> 

I grep 'virtio_break_device' in the latest code:
arch/um/drivers/virtio_uml.c:1147:	virtio_break_device(&vu_dev->vdev);
arch/um/drivers/virtio_uml.c:1285:	virtio_break_device(&vu_dev->vdev);
drivers/crypto/virtio/virtio_crypto_core.c:269:	 
virtio_break_device(vcrypto->vdev);
drivers/s390/virtio/virtio_ccw.c:1251:			virtio_break_device(&vcdev->vdev);
drivers/s390/virtio/virtio_ccw.c:1268:		virtio_break_device(&vcdev->vdev);
drivers/firmware/arm_scmi/virtio.c:489: 
virtio_break_device(vioch->vqueue->vdev);
drivers/char/virtio_console.c:1956:	virtio_break_device(vdev);

Some virtio drivers use 'virtio_break_device'...

>>>>>> - virtqueue_get_desc_addr/virtqueue_get_avail_addr/virtqueue_get_used_addr
>>>>>>      /virtqueue_get_vring is vring specific, I'd like to rename them like
>>>>>>      vring_virtqueue_get_desc_addr. Is this reasonable?
>>>>>> - there are still some functions in virtio_ring.c with prefix *virtqueue*,
>>>>>>      for example 'virtqueue_add_split', just keep it or rename it to
>>>>>>      'vring_virtqueue_add_split'?
>>>>>> zhenwei pi (2):
>>>>>>      virtio: abstract virtqueue related methods
>>>>>>      tools/virtio: implement virtqueue in test
>>>>>>
>>>>>>     drivers/virtio/virtio_ring.c | 285 +++++-----------------
>>>>>>     include/linux/virtio.h       | 441 +++++++++++++++++++++++++++++++----
>>>>>>     include/linux/virtio_ring.h  |  26 +++
>>>>>>     tools/virtio/linux/virtio.h  | 355 +++++++++++++++++++++++++---
>>>>>>     4 files changed, 807 insertions(+), 300 deletions(-)
>>>>>>
>>>>>> -- 
>>>>>> 2.20.1
>>>>>
>>>>
>>>> -- 
>>>> zhenwei pi
>>>
>>
>> -- 
>> zhenwei pi
> 

-- 
zhenwei pi