netdev - Re: [PATCH] vhost-net: support VIRTIO_F_RING

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Date:   Mon, 5 Sep 2022 16:32:19 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Kangjie Xu <kangjie.xu@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org
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, xuanzhuo@...ux.alibaba.com
Subject: Re: [PATCH] vhost-net: support VIRTIO_F_RING_RESET


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>


> ---
>
> 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 {