Re: [RFC v2 5/7] vhost: Add x-vhost-enable-shadow-vq qmp

From: Stefan Hajnoczi <stefanha@redhat.com>
To: "Eugenio Pérez" <eperezma@redhat.com>
Cc: Rob Miller <rob.miller@broadcom.com>,
	Parav Pandit <parav@mellanox.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, Harpreet Singh Anand <hanand@xilinx.com>,
	Xiao W Wang <xiao.w.wang@intel.com>, Eli Cohen <eli@mellanox.com>,
	virtualization@lists.linux-foundation.org,
	Eric Blake <eblake@redhat.com>, Michael Lilja <ml@napatech.com>,
	Jim Harford <jim.harford@broadcom.com>
Subject: Re: [RFC v2 5/7] vhost: Add x-vhost-enable-shadow-vq qmp
Date: Wed, 17 Feb 2021 15:26:33 +0000	[thread overview]
Message-ID: <20210217152633.GG269203@stefanha-x1.localdomain> (raw)
In-Reply-To: <20210209153757.1653598-6-eperezma@redhat.com>

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On Tue, Feb 09, 2021 at 04:37:55PM +0100, Eugenio Pérez wrote:
> diff --git a/qapi/net.json b/qapi/net.json
> index c31748c87f..a1cdffb0f9 100644
> --- a/qapi/net.json
> +++ b/qapi/net.json
> @@ -77,6 +77,28 @@
>  ##
>  { 'command': 'netdev_del', 'data': {'id': 'str'} }
>  
> +##
> +# @x-vhost-enable-shadow-vq:
> +#
> +# Use vhost shadow virtqueue.

Is this command for testing only or do you expect it to be invoked by
libvirt in production? I think the shadow virtqueue can be an internal
QEMU feature that is hidden from management tools.

> +#
> +# @name: the device name of the virtual network adapter
> +#
> +# @enable: true to use he alternate shadow VQ notification path
> +#
> +# Returns: Error if failure, or 'no error' for success
> +#
> +# Since: 6.0

Is this a generic feature for any vhost or vDPA device? If yes, please
replace "virtual network adapter" in the doc comment.

Does this only apply to vhost-net devices? If so, please put "vhost-net"
in the name since there are other non-net vhost devices.

> +#
> +# Example:
> +#
> +# -> { "execute": "x-vhost-enable-shadow-vq", "arguments": {"enable": true} }

Missing "name" field?

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