linux-kernel - Re: [PATCH 3/3] virtio-gpu api: VIRTIO_GPU_F_RESSOURCE

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Date:   Thu, 11 Apr 2019 07:03:22 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Gurchetan Singh <gurchetansingh@...omium.org>
Cc:     ML dri-devel <dri-devel@...ts.freedesktop.org>,
        virtio@...ts.oasis-open.org, David Airlie <airlied@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Marc-André Lureau <marcandre.lureau@...il.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Jason Wang <jasowang@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        "open list:VIRTIO CORE, NET AND BLOCK DRIVERS" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] virtio-gpu api: VIRTIO_GPU_F_RESSOURCE_V2

> > +/* VIRTIO_GPU_CMD_RESOURCE_CREATE_V2 */
> > +struct virtio_gpu_cmd_resource_create_v2 {
> > +       struct virtio_gpu_ctrl_hdr hdr;
> > +       __le32 resource_id;
> > +       __le32 format;
> > +       __le32 width;
> > +       __le32 height;
> > +       /* 3d only */
> > +       __le32 target;
> > +       __le32 bind;
> > +       __le32 depth;
> > +       __le32 array_size;
> > +       __le32 last_level;
> > +       __le32 nr_samples;
> > +       __le32 flags;
> > +};
> 
> 
> I assume this is always backed by some host side allocation, without any
> guest side pages associated with it?

No.  It is not backed at all yet.  Workflow would be like this:

  (1) VIRTIO_GPU_CMD_RESOURCE_CREATE_V2
  (2) VIRTIO_GPU_CMD_MEMORY_CREATE (see patch 2)
  (3) VIRTIO_GPU_CMD_RESOURCE_MEMORY_ATTACH (see patch 2)

You could also create a larger pool with VIRTIO_GPU_CMD_MEMORY_CREATE,
then go attach multiple resources to it.

> If so, do we want the option for the guest allocate?

Allocation options are handled by VIRTIO_GPU_CMD_MEMORY_CREATE
(initially guest allocated only, i.e. what virtio-gpu supports today,
the plan is to add other allocation types later on).

> > +/* VIRTIO_GPU_RESP_OK_RESOURCE_INFO */
> > +struct virtio_gpu_resp_resource_info {
> > +       struct virtio_gpu_ctrl_hdr hdr;
> > +       __le32 stride[4];
> > +       __le32 size[4];
> > +};
> 
> offsets[4] needed too

That is in VIRTIO_GPU_CMD_RESOURCE_MEMORY_ATTACH ...

cheers,
  Gerd