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

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Message-ID: <20230517020947-mutt-send-email-mst@kernel.org>
Date:   Wed, 17 May 2023 02:10:18 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     zhenwei pi <pizhenwei@...edance.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: [PATCH v2 0/2] virtio: abstract virtqueue related methods

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.

> > > > > - 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