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    SubjectRe: [PATCH v18 5/6] vfio: ABI for mdev display dma-buf operation
    On Thu, 16 Nov 2017 11:21:56 +0800
    Zhenyu Wang <zhenyuw@linux.intel.com> wrote:

    > On 2017.11.15 11:48:42 -0700, Alex Williamson wrote:
    > > On Wed, 15 Nov 2017 17:11:54 +0800
    > > Tina Zhang <tina.zhang@intel.com> wrote:
    > >
    > > > Add VFIO_DEVICE_QUERY_GFX_PLANE ioctl command to let user query and get
    > > > a plane and its information. So far, two types of buffers are supported:
    > > > buffers based on dma-buf and buffers based on region.
    > > >
    > > > This ioctl can be invoked with:
    > > > 1) Either DMABUF or REGION flag. Vendor driver returns a plane_info
    > > > successfully only when the specific kind of buffer is supported.
    > > > 2) Flag PROBE. And at the same time either DMABUF or REGION must be set,
    > > > so that vendor driver returns success only when the specific kind of
    > > > buffer is supported.
    > > >
    > > > Add VFIO_DEVICE_GET_GFX_DMABUF ioctl command to let user get a specific
    > > > dma-buf fd of an exposed MDEV buffer provided by dmabuf_id which was
    > > > returned in VFIO_DEVICE_QUERY_GFX_PLANE ioctl command.
    > > >
    > > > The life cycle of an exposed MDEV buffer is handled by userspace and
    > > > tracked by kernel space. The returned dmabuf_id in struct vfio_device_
    > > > query_gfx_plane can be a new id of a new exposed buffer or an old id of
    > > > a re-exported buffer. Host user can check the value of dmabuf_id to see
    > > > if it needs to create new resources according to the new exposed buffer
    > > > or just re-use the existing resource related to the old buffer.
    > > >
    > > > v18:
    > > > - update comments for VFIO_DEVICE_GET_GFX_DMABUF. (Alex)
    > > >
    > > > v17:
    > > > - modify VFIO_DEVICE_GET_GFX_DMABUF interface. (Alex)
    > > >
    > > > v16:
    > > > - add x_hot and y_hot fields. (Gerd)
    > > > - add comments for VFIO_DEVICE_GET_GFX_DMABUF. (Alex)
    > > > - rebase to 4.14.0-rc6.
    > > >
    > > > v15:
    > > > - add a ioctl to get a dmabuf for a given dmabuf id. (Gerd)
    > > >
    > > > v14:
    > > > - add PROBE, DMABUF and REGION flags. (Alex)
    > > >
    > > > v12:
    > > > - add drm_format_mod back. (Gerd and Zhenyu)
    > > > - add region_index. (Gerd)
    > > >
    > > > v11:
    > > > - rename plane_type to drm_plane_type. (Gerd)
    > > > - move fields of vfio_device_query_gfx_plane to vfio_device_gfx_plane_info.
    > > > (Gerd)
    > > > - remove drm_format_mod, start fields. (Daniel)
    > > > - remove plane_id.
    > > >
    > > > v10:
    > > > - refine the ABI API VFIO_DEVICE_QUERY_GFX_PLANE. (Alex) (Gerd)
    > > >
    > > > v3:
    > > > - add a field gvt_plane_info in the drm_i915_gem_obj structure to save
    > > > the decoded plane information to avoid look up while need the plane
    > > > info. (Gerd)
    > > >
    > > > Signed-off-by: Tina Zhang <tina.zhang@intel.com>
    > > > Cc: Gerd Hoffmann <kraxel@redhat.com>
    > > > Cc: Alex Williamson <alex.williamson@redhat.com>
    > > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
    > > > ---
    > > > include/uapi/linux/vfio.h | 62 +++++++++++++++++++++++++++++++++++++++++++++++
    > > > 1 file changed, 62 insertions(+)
    > > >
    > > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
    > > > index ae46105..5c1cca2 100644
    > > > --- a/include/uapi/linux/vfio.h
    > > > +++ b/include/uapi/linux/vfio.h
    > > > @@ -502,6 +502,68 @@ struct vfio_pci_hot_reset {
    > > >
    > > > #define VFIO_DEVICE_PCI_HOT_RESET _IO(VFIO_TYPE, VFIO_BASE + 13)
    > > >
    > > > +/**
    > > > + * VFIO_DEVICE_QUERY_GFX_PLANE - _IOW(VFIO_TYPE, VFIO_BASE + 14,
    > > > + * struct vfio_device_query_gfx_plane)
    > > > + *
    > > > + * Set the drm_plane_type and flags, then retrieve the gfx plane info.
    > > > + *
    > > > + * flags supported:
    > > > + * - VFIO_GFX_PLANE_TYPE_PROBE and VFIO_GFX_PLANE_TYPE_DMABUF are set
    > > > + * to ask if the mdev supports dma-buf. 0 on support, -EINVAL on no
    > > > + * support for dma-buf.
    > > > + * - VFIO_GFX_PLANE_TYPE_PROBE and VFIO_GFX_PLANE_TYPE_REGION are set
    > > > + * to ask if the mdev supports region. 0 on support, -EINVAL on no
    > > > + * support for region.
    > > > + * - VFIO_GFX_PLANE_TYPE_DMABUF or VFIO_GFX_PLANE_TYPE_REGION is set
    > > > + * with each call to query the plane info.
    > > > + * - Others are invalid and return -EINVAL.
    > > > + *
    > > > + * Note:
    > > > + * 1. Plane could be disabled by guest. In that case, success will be
    > > > + * returned with zero-initialized drm_format, size, width and height
    > > > + * fields.
    > > > + * 2. x_hot/y_hot is set to 0xFFFFFFFF if no hotspot information available
    > > > + *
    > > > + * Return: 0 on success, -errno on other failure.
    > > > + */
    > > > +struct vfio_device_gfx_plane_info {
    > > > + __u32 argsz;
    > > > + __u32 flags;
    > > > +#define VFIO_GFX_PLANE_TYPE_PROBE (1 << 0)
    > > > +#define VFIO_GFX_PLANE_TYPE_DMABUF (1 << 1)
    > > > +#define VFIO_GFX_PLANE_TYPE_REGION (1 << 2)
    > > > + /* in */
    > > > + __u32 drm_plane_type; /* type of plane: DRM_PLANE_TYPE_* */
    > > > + /* out */
    > > > + __u32 drm_format; /* drm format of plane */
    > > > + __u64 drm_format_mod; /* tiled mode */
    > > > + __u32 width; /* width of plane */
    > > > + __u32 height; /* height of plane */
    > > > + __u32 stride; /* stride of plane */
    > > > + __u32 size; /* size of plane in bytes, align on page*/
    > > > + __u32 x_pos; /* horizontal position of cursor plane */
    > > > + __u32 y_pos; /* vertical position of cursor plane*/
    > > > + __u32 x_hot; /* horizontal position of cursor hotspot */
    > > > + __u32 y_hot; /* vertical position of cursor hotspot */
    > > > + union {
    > > > + __u32 region_index; /* region index */
    > > > + __u32 dmabuf_id; /* dma-buf id */
    > > > + };
    > > > +};
    > > > +
    > > > +#define VFIO_DEVICE_QUERY_GFX_PLANE _IO(VFIO_TYPE, VFIO_BASE + 14)
    > > > +
    > > > +/**
    > > > + * VFIO_DEVICE_GET_GFX_DMABUF - _IOW(VFIO_TYPE, VFIO_BASE + 15, __u32)
    > > > + *
    > > > + * Return a new dma-buf file descriptor for an exposed guest framebuffer
    > > > + * described by the provided dmabuf_id. The dmabuf_id is returned from VFIO_
    > > > + * DEVICE_QUERY_GFX_PLANE as a token of the exposed guest framebuffer.
    > > > + */
    > > > +
    > > > +#define VFIO_DEVICE_GET_GFX_DMABUF _IO(VFIO_TYPE, VFIO_BASE + 15)
    > > > +
    > > > /* -------- API for Type1 VFIO IOMMU -------- */
    > > >
    > > > /**
    > >
    > > Looks good to me. Kirti, have you had a chance yet to verify this is
    > > sufficient for your region-based approach? It would be great to get
    > > confirmation of that ASAP so we can get this in. Thanks,
    > >
    >
    > Alex, do you mind by merging this just through gvt tree? Or you would
    > like to merge this then send pull request for us then we can apply left?

    I'm fine with this going through the gvt tree, but I want some
    confirmation from nvidia that this meets their needs as well before I
    provide an ack. Thanks,

    Alex

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