[PATCH 1/1] vhost: support VIRTIO_F_RING_RESET for vhost-user

[Kangjie Xu]

This patch will be updated in the future. We'll fix some issues based on 
some review comments from QEMU community.

We intend to add a new vhost protocol message for virtqueue reset.

Please let me know any questions or suggestions you might have.

Thanks

在 2022/7/19 15:26, 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
>      https://github.com/oasis-tcs/virtio-spec/issues/124
>      https://github.com/oasis-tcs/virtio-spec/issues/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,
> VHOST_USER_SET_VRING_ENABLE message with "payload.state.num" set to 0
> is sent to DPDK. Then the virtqueue will be disabled in DPDK.
> 2. After the virtqueue is disabled, the driver may optionally re-enable
> it. To avoid confusion with VHOST_USER_SET_VRING_ENABLE, we call this
> part as "restart". The virtqueue's information may be changed when
> restarting it. Thus, the information of the reset virtqueue should be
> updated. This part is basically similar to when the virtqueue is started
> for the first time, except that the restart process does not need to set
> features and set mem table since they does not change. QEMU will send
> messages containing size, base, addr, kickfd and callfd of the virtqueue
> in order. Specifically, the DPDK will receive these messages in order:
>      a. VHOST_USER_SET_VRING_NUM
>      b. VHOST_USER_SET_VRING_BASE
>      c. VHOST_USER_SET_VRING_ADDR
>      d. VHOST_USER_SET_VRING_KICK
>      e. VHOST_USER_SET_VRING_CALL
>      f. VHOST_USER_SET_VRING_ENABLE
> The last VHOST_USER_SET_VRING_ENABLE message with "payload.state.num" set
> to 1, will be sent to enable the virtqueue and the restart process is
> finished.
>
> Signed-off-by: Kangjie Xu <kangjie.xu at linux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> ---
> Test environment:
>      Host: 5.4.189
>      Qemu: QEMU emulator version 7.0.50 (With vq reset support)
>      Guest: 5.19.0-rc3 (With vq reset support)
>      DPDK: 22.07-rc1
>      Test Cmd: ethtool -g eth1; ethtool -G eth1 rx $1 tx $2;
>              ethtool -g eth1;
>
>      The driver can resize the virtio queue, then virtio queue reset
>      function should be triggered.
>
> Guest Kernel Patch:
>      https://lore.kernel.org/bpf/20220629065656.54420-1-xuanzhuo@linux.alibaba.com
>
> QEMU Patch:
>      https://lore.kernel.org/qemu-devel/cover.1658141552.git.kangjie.xu@linux.alibaba.com
>
>   lib/vhost/vhost.h | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index 14235aaf81..9711ded7dd 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -378,6 +378,11 @@ struct vhost_msg {
>    #define VIRTIO_F_VERSION_1 32
>   #endif
>   
> +/* This feature indicates that the driver can reset a queue individually. */
> +#ifndef VIRTIO_F_RING_RESET
> +#define VIRTIO_F_RING_RESET 40
> +#endif
> +
>   /* Declare packed ring related bits for older kernels */
>   #ifndef VIRTIO_F_RING_PACKED
>   
> @@ -440,7 +445,8 @@ struct vring_packed_desc_event {
>   				(1ULL << VIRTIO_NET_F_MTU)  | \
>   				(1ULL << VIRTIO_F_IN_ORDER) | \
>   				(1ULL << VIRTIO_F_IOMMU_PLATFORM) | \
> -				(1ULL << VIRTIO_F_RING_PACKED))
> +				(1ULL << VIRTIO_F_RING_PACKED)	| \
> +				(1ULL << VIRTIO_F_RING_RESET))
>   
>   
>   struct guest_page {