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Date: Tue, 11 Jul 2017 10:47:24 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 06/10] pc-bios/s390-ccw: Add code for
 virtio feature negotiation
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To: Thomas Huth <thuth@redhat.com>
Cc: qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@de.ibm.com>, Alexander Graf <agraf@suse.de>, Farhan Ali <alifm@linux.vnet.ibm.com>, David Hildenbrand <david@redhat.com>, Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>, Alexey Kardashevskiy <aik@ozlabs.ru>

On Mon, 10 Jul 2017 17:32:36 +0200
Thomas Huth <thuth@redhat.com> wrote:

> The upcoming virtio-net driver needs to negotiate some features,
> so we need the possibility to do this in the core virtio code.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  pc-bios/s390-ccw/s390-ccw.h      |  2 ++
>  pc-bios/s390-ccw/virtio-blkdev.c |  3 ++-
>  pc-bios/s390-ccw/virtio.c        | 25 ++++++++++++++++++-------
>  pc-bios/s390-ccw/virtio.h        |  2 +-
>  4 files changed, 23 insertions(+), 9 deletions(-)
> 

> diff --git a/pc-bios/s390-ccw/virtio-blkdev.c b/pc-bios/s390-ccw/virtio-blkdev.c
> index 6cb77bc..ed4026f 100644
> --- a/pc-bios/s390-ccw/virtio-blkdev.c
> +++ b/pc-bios/s390-ccw/virtio-blkdev.c
> @@ -266,9 +266,10 @@ uint64_t virtio_get_blocks(void)
>  void virtio_blk_setup_device(SubChannelId schid)
>  {
>      VDev *vdev = virtio_get_device();
> +    uint32_t guestfeats[2] = { 0, 0 };
>  
>      vdev->schid = schid;
> -    virtio_setup_ccw(vdev);
> +    virtio_setup_ccw(vdev, guestfeats);

I'd tack the feature bits onto the VDev instead. Even if you're not
doing anything fancy right now, it makes validating the feature bits
more straightforward.

>  
>      switch (vdev->senseid.cu_model) {
>      case VIRTIO_ID_BLOCK: