On 05/25/2015 01:28 AM, Tetsuya Mukawa wrote: > This patch adds 'backend_features' option for vhost-user backends. > If this option is specified, QEMU assumes vhost-user backends support > the features specified by user, and QEMU can start without vhost-user > backend. > > Here are examples. > * QEMU is configured as vhost-user client. > -chardev socket,id=chr0,path=/tmp/sock,reconnect=3 \ > -netdev vhost-user,id=net0,chardev=chr0,vhostforce,backend_features=0x68000 \ > -device virtio-net-pci,netdev=net0 \ > > * QEMU is configured as vhost-user server. > -chardev socket,id=chr0,path=/tmp/sock,server,nowait \ > -netdev vhost-user,id=net0,chardev=chr0,vhostforce,backend_features=0x68000 \ > -device virtio-net-pci,netdev=net0 \ > > To know vhost-user backend features that the backend expects, please > specify 0xffffffff as backend_features, then invoke QEMU and check error log > like below. > > Lack of backend features. Expected 0xffffffff, but receives 0x68000 > > Above log indicates the backend features QEMU should be passed. > > Signed-off-by: Tetsuya Mukawa <muk...@igel.co.jp> > ---
> +++ b/qapi-schema.json
> @@ -2243,6 +2243,8 @@
> #
> # @queues: #optional number of queues to be created for multiqueue capable
> tap
> #
> +# @backend_features: #optional feature flag to support vhost user backend
Missing a (since 2.4) designation.
New interfaces should prefer - over _, but I see that you are consistent
with vnet_hder already in this struct so it is okay.
> +#
> # Since 1.2
> ##
> { 'struct': 'NetdevTapOptions',
> @@ -2259,7 +2261,8 @@
> '*vhostfd': 'str',
> '*vhostfds': 'str',
> '*vhostforce': 'bool',
> - '*queues': 'uint32'} }
> + '*queues': 'uint32',
> + '*backend_features':'uint64'} }
Ewww. Making users figure out what integers to pass is NOT user
friendly. Better would be an enum type, and make the parameter an
optional array of enum values.
>
> ##
> # @NetdevSocketOptions
> @@ -2444,12 +2447,15 @@
> #
> # @vhostforce: #optional vhost on for non-MSIX virtio guests (default:
> false).
> #
> +# @backend_features: #optional feature flag to support vhost user backend
> (default: 0).
> +#
Long line. Please wrap to fit within 80 columns. Missing (since 2.4)
deisgnation. Again, I don't like making users know a raw integer; an
enum type would be better.
> # Since 2.1
> ##
> { 'struct': 'NetdevVhostUserOptions',
> 'data': {
> 'chardev': 'str',
> - '*vhostforce': 'bool' } }
> + '*vhostforce': 'bool',
> + '*backend_features': 'uint64' } }
This struct has no pre-existing _, so the name 'backend-features' is nicer.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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