Re: [Qemu-devel] [PATCH] vhost-vsock: support parse mergeable feature

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Dec 13, 2018 at 11:27:24AM +0800, jiangyiwen wrote:
> On 2018/12/12 21:19, Michael S. Tsirkin wrote:
> > On Wed, Dec 12, 2018 at 05:54:49PM +0800, jiangyiwen wrote:
> >> Currently vhost-vsock doesn't have any feature bits, so it
> >> don't support parse mergeable rx buffer feature. And the
> >> feature is support in another series of patches named
> >> "VSOCK: support mergeable rx buffer in vhost-vsock".
> >>
> >> So we neet to support parse mergeable feature in vhost-vsock
> >> if above patches are merged.
> >>
> >> Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
> > 
> > OK but what does it do? this just defines the feature bit ...
> > Also pls copy virtio-dev whenever you change the host/guest
> > interface.
> > 
> > Thanks!
> > 
> 
> Hi Michael,
> 
> In my opinion, for vhost device, device feature bits need to be
> intersected between vhost and qemu, so I add mergeable rx buffer feature
> into vdev->host_features, and then intersected with vhost_dev features.
> 
> Later if someone want to add new feature, it can use virtio_add_feature()
> in vhost_vsock_get_features().
> 
> Thanks,
> Yiwen.

I understand. Sorry.  It seems that your patchset wasn't threaded
properly, each patch was by its own. Can you pls take a look at fixing
that?

> >> ---
> >>  hw/virtio/vhost-vsock.c                       | 9 +++++++--
> >>  include/standard-headers/linux/virtio_vsock.h | 3 +++
> >>  2 files changed, 10 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> >> index aa5af92..5023c05 100644
> >> --- a/hw/virtio/vhost-vsock.c
> >> +++ b/hw/virtio/vhost-vsock.c
> >> @@ -178,8 +178,13 @@ static uint64_t vhost_vsock_get_features(VirtIODevice *vdev,
> >>                                           uint64_t requested_features,
> >>                                           Error **errp)
> >>  {
> >> -    /* No feature bits used yet */
> >> -    return requested_features;
> >> +    VHostVSock *vsock = VHOST_VSOCK(vdev);
> >> +    uint64_t features;
> >> +
> >> +    virtio_add_feature(&requested_features, VIRTIO_VSOCK_F_MRG_RXBUF);
> >> +    features = requested_features & vsock->vhost_dev.features;
> >> +
> >> +    return features;
> >>  }
> >>
> >>  static void vhost_vsock_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> >> diff --git a/include/standard-headers/linux/virtio_vsock.h b/include/standard-headers/linux/virtio_vsock.h
> >> index be44321..4c583ec 100644
> >> --- a/include/standard-headers/linux/virtio_vsock.h
> >> +++ b/include/standard-headers/linux/virtio_vsock.h
> >> @@ -38,6 +38,9 @@
> >>  #include "standard-headers/linux/virtio_ids.h"
> >>  #include "standard-headers/linux/virtio_config.h"
> >>
> >> +/* Virtio-vsock feature */
> >> +#define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
> >> +
> >>  struct virtio_vsock_config {
> >>  	uint64_t guest_cid;
> >>  } QEMU_PACKED;
> >> -- 
> >> 1.8.3.1
> >>
> > 
> > .
> > 
>