linux-kernel - Re: [PATCH] vhost-net: support VIRTIO_F_RING

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Date:   Mon, 30 Jan 2023 05:29:41 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, hengqi@...ux.alibaba.com,
        Kangjie Xu <kangjie.xu@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] vhost-net: support VIRTIO_F_RING_RESET

On Mon, Jan 30, 2023 at 03:39:06PM +0800, Xuan Zhuo wrote:
> On Mon, 5 Sep 2022 16:32:19 +0800, Jason Wang <jasowang@...hat.com> wrote:
> >
> > 在 2022/8/25 16:56, Kangjie Xu 写道:
> > > Add VIRTIO_F_RING_RESET, which indicates that the driver can reset a
> > > queue individually.
> > >
> > > VIRTIO_F_RING_RESET feature is added to virtio-spec 1.2. The relevant
> > > information is in
> > >      oasis-tcs/virtio-spec#124
> > >      oasis-tcs/virtio-spec#139
> > >
> > > The implementation only adds the feature bit in supported features. It
> > > does not require any other changes because we reuse the existing vhost
> > > protocol.
> > >
> > > The virtqueue reset process can be concluded as two parts:
> > > 1. The driver can reset a virtqueue. When it is triggered, we use the
> > > set_backend to disable the virtqueue.
> > > 2. After the virtqueue is disabled, the driver may optionally re-enable
> > > it. The process is basically similar to when the device is started,
> > > except that the restart process does not need to set features and set
> > > mem table since they do not change. QEMU will send messages containing
> > > size, base, addr, kickfd and callfd of the virtqueue in order.
> > > Specifically, the host kernel will receive these messages in order:
> > >      a. VHOST_SET_VRING_NUM
> > >      b. VHOST_SET_VRING_BASE
> > >      c. VHOST_SET_VRING_ADDR
> > >      d. VHOST_SET_VRING_KICK
> > >      e. VHOST_SET_VRING_CALL
> > >      f. VHOST_NET_SET_BACKEND
> > > Finally, after we use set_backend to attach the virtqueue, the virtqueue
> > > will be enabled and start to work.
> > >
> > > Signed-off-by: Kangjie Xu <kangjie.xu@...ux.alibaba.com>
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> >
> >
> > Acked-by: Jason Wang <jasowang@...hat.com>
> 
> @mst
> 
> Do we miss this?
> 
> Thanks.

I did, thanks! tagged now.

> >
> >
> > > ---
> > >
> > > Test environment and method:
> > >      Host: 5.19.0-rc3
> > >      Qemu: QEMU emulator version 7.0.50 (With vq rset support)
> > >      Guest: 5.19.0-rc3 (With vq reset support)
> > >      Test Cmd: ethtool -g eth1; ethtool -G eth1 rx $1 tx $2; ethtool -g eth1;
> > >
> > >      The drvier can resize the virtio queue, then virtio queue reset function should
> > >      be triggered.
> > >
> > >      The default is split mode, modify Qemu virtio-net to add PACKED feature to
> > >      test packed mode.
> > >
> > > Guest Kernel Patch:
> > >      https://lore.kernel.org/bpf/20220801063902.129329-1-xuanzhuo@linux.alibaba.com/
> > >
> > > QEMU Patch:
> > >      https://lore.kernel.org/qemu-devel/cover.1661414345.git.kangjie.xu@linux.alibaba.com/
> > >
> > > Looking forward to your review and comments. Thanks.
> > >
> > >   drivers/vhost/net.c | 3 ++-
> > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > > index 68e4ecd1cc0e..8a34928d4fef 100644
> > > --- a/drivers/vhost/net.c
> > > +++ b/drivers/vhost/net.c
> > > @@ -73,7 +73,8 @@ enum {
> > >   	VHOST_NET_FEATURES = VHOST_FEATURES |
> > >   			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
> > >   			 (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
> > > -			 (1ULL << VIRTIO_F_ACCESS_PLATFORM)
> > > +			 (1ULL << VIRTIO_F_ACCESS_PLATFORM) |
> > > +			 (1ULL << VIRTIO_F_RING_RESET)
> > >   };
> > >
> > >   enum {
> >