linux-kernel - Re: [PATCH v4 00/14] virtio pci support VIRTIO_F_RING

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Date:   Fri, 11 Feb 2022 15:09:35 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v4 00/14] virtio pci support VIRTIO_F_RING_RESET

On Fri, Feb 11, 2022 at 2:34 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Fri, 11 Feb 2022 13:40:52 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Wed, Feb 9, 2022 at 8:29 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > >
> > > The virtio spec already supports the virtio queue reset function. This patch set
> > > is to add this function to the kernel. The relevant virtio spec information is
> > > here:
> > >
> > >     https://github.com/oasis-tcs/virtio-spec/issues/124
> > >
> > > Also regarding MMIO support for queue reset, I plan to support it after this
> > > patch is passed.
> >
> > So I had an idea, we can implement ethtool_set_ringparam() in this
> > series to get one real users.
>
> I agree, in fact my local test is using this feature.

Right.

>
> >
> > But this came into another question: it looks to me current virito-net
> > just uses the maximum ring size, so it basically means we just can
> > decrease the number from startup, so I wonder how much value if we
> > don't limit the startup queue size to a dedicated value.
>
> I also have this consideration, so I want to add a virtio-net module parameter
> to specify an initial value.

But module parameters are not user friendly. Let it be changed via
ethtool should be sufficient.

>
> This initial value also has another meaning. In order to achieve high
> performance, the backend can provide a large ring size capability, but we also
> hope that the ring size can only be increased through ethtool -G when the user
> needs it.
>
> To implement this function, we need to add a new parameter to find_vqs().
>
> If there is no problem, I will bring this function in the next version.

I think so, and we need to choose a sane default value. I guess
something up to 1024 should be sufficient.

Thanks

>
> Thannks.
>
>
> >
> > Thanks
> >
> > >
> > > Please review. Thanks.
> > >
> > > v4:
> > >   1. just the code of virtio, without virtio-net
> > >   2. Performing reset on a queue is divided into these steps:
> > >     1. reset_vq: reset one vq
> > >     2. recycle the buffer from vq by virtqueue_detach_unused_buf()
> > >     3. release the ring of the vq by vring_release_virtqueue()
> > >     4. enable_reset_vq: re-enable the reset queue
> > >   3. Simplify the parameters of enable_reset_vq()
> > >   4. add container structures for virtio_pci_common_cfg
> > >
> > > v3:
> > >   1. keep vq, irq unreleased
> > >
> > > Xuan Zhuo (14):
> > >   virtio_pci: struct virtio_pci_common_cfg add queue_notify_data
> > >   virtio: queue_reset: add VIRTIO_F_RING_RESET
> > >   virtio_ring: queue_reset: add function vring_setup_virtqueue()
> > >   virtio_ring: queue_reset: split: add __vring_init_virtqueue()
> > >   virtio_ring: queue_reset: split: support enable reset queue
> > >   virtio_ring: queue_reset: packed: support enable reset queue
> > >   virtio_ring: queue_reset: extract the release function of the vq ring
> > >   virtio_ring: queue_reset: add vring_release_virtqueue()
> > >   virtio: queue_reset: struct virtio_config_ops add callbacks for
> > >     queue_reset
> > >   virtio_pci: queue_reset: update struct virtio_pci_common_cfg and
> > >     option functions
> > >   virtio_pci: queue_reset: release vq by vp_dev->vqs
> > >   virtio_pci: queue_reset: setup_vq() support vring_setup_virtqueue()
> > >   virtio_pci: queue_reset: vp_setup_vq() support ring_num
> > >   virtio_pci: queue_reset: support VIRTIO_F_RING_RESET
> > >
> > >  drivers/virtio/virtio_pci_common.c     |  65 +++++++---
> > >  drivers/virtio/virtio_pci_common.h     |  11 +-
> > >  drivers/virtio/virtio_pci_legacy.c     |   5 +-
> > >  drivers/virtio/virtio_pci_modern.c     |  99 ++++++++++++--
> > >  drivers/virtio/virtio_pci_modern_dev.c |  36 +++++
> > >  drivers/virtio/virtio_ring.c           | 173 ++++++++++++++++++-------
> > >  include/linux/virtio.h                 |   6 +
> > >  include/linux/virtio_config.h          |  13 ++
> > >  include/linux/virtio_pci_modern.h      |   2 +
> > >  include/linux/virtio_ring.h            |  37 ++++--
> > >  include/uapi/linux/virtio_config.h     |   7 +-
> > >  include/uapi/linux/virtio_pci.h        |  14 ++
> > >  12 files changed, 375 insertions(+), 93 deletions(-)
> > >
> > > --
> > > 2.31.0
> > >
> >
>