RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations

[Zhang, Tina]

Hi,

Thanks for all the comments. Here are the summaries:

1. Modify the structures to make it more general.
struct vfio_device_gfx_plane_info {
	__u64 start;
	__u64 drm_format_mod;
	__u32 drm_format;
	__u32 width;
	__u32 height;
	__u32 stride;
	__u32 size;
	__u32 x_pos;
	__u32 y_pos;
	__u32 generation;
};
struct vfio_device_query_gfx_plane {
	__u32 argsz;
	__u32 flags;
#define VFIO_GFX_PLANE_FLAGS_REGION_ID		(1 << 0)
#define VFIO_GFX_PLANE_FLAGS_PLANE_ID		(1 << 1)
	struct vfio_device_gfx_plane_info plane_info;
	__u32 id; 
};
2. Remove dmabuf mgr fd and add these two ioctl commands to the vfio device fd.
VFIO_DEVICE_QUERY_GFX_PLANE : used to query vfio_device_gfx_plane_info.
VFIO_DEVICE_GET_DMABUF_FD: used to create and return the dmabuf fd.

Am I correct? Thanks.

Tina


> -----Original Message-----
> From: Intel-gfx [mailto:intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of
> Alex Williamson
> Sent: Monday, June 19, 2017 10:56 PM
> To: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Kirti
> Wankhede <kwankhede@xxxxxxxxxx>; Chen, Xiaoguang
> <xiaoguang.chen@xxxxxxxxx>; intel-gvt-dev@xxxxxxxxxxxxxxxxxxxxx; Lv, Zhiyuan
> <zhiyuan.lv@xxxxxxxxx>
> Subject: Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf
> operations
> 
> On Mon, 19 Jun 2017 08:38:32 +0200
> Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
> 
> >   Hi,
> >
> > > My suggestion was to use vfio device fd for this ioctl and have
> > > dmabuf mgr fd as member in above query_plane structure, for region
> > > type it would be set to 0.
> >
> > Region type should be DRM_PLANE_TYPE_PRIMARY
> >
> > > Can't mmap that page to get surface information. There is no way to
> > > synchronize between QEMU reading this mmapped region and vendor
> > > driver writing it. There could be race condition in these two
> > > operations.
> > > Read
> > > on this page should be trapped and blocking, so that surface in that
> > > region is only updated when its asked for.
> >
> > Does it make sense to have a "generation" field in the plane_info
> > struct (which gets increased each time the struct changes) ?
> 
> It seems less cumbersome than checking each field to see if it has changed.
> Thanks,
> 
> Alex
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