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

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Date:   Mon, 30 Jan 2023 15:39:06 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...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, 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.

>
>
> > ---
> >
> > 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 {
>