Hi Eric,
On 月, 2015-05-25 at 16:11 -0600, Eric Blake wrote:
> 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.
Thanks for your comments.
I guess below may be good example. Is this same as your suggestion?
virtio-net-pci,netdev=hostnet3,id=net3,gso=off,guest_tso4=off,guest_tso6=off
So I will improve 'backend-features' like below.
backend-features=gso=off,guest_tso4=off,guest_tso6=off
Also I will fix 'qapi-schema.json' to work like above.
>
> >
> > ##
> > # @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.
I will fix it in v2 patch.
> 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.
>
Also I will fix it.
Regards,
Tetsuya
