On Tue, 20 Jun 2017 23:01:53 +0000 "Zhang, Tina" <tina.zh...@intel.com> wrote:
> > -----Original Message----- > > From: Alex Williamson [mailto:alex.william...@redhat.com] > > Sent: Tuesday, June 20, 2017 11:00 PM > > To: Gerd Hoffmann <kra...@redhat.com> > > Cc: Zhang, Tina <tina.zh...@intel.com>; intel-gfx@lists.freedesktop.org; > > linux- > > ker...@vger.kernel.org; Kirti Wankhede <kwankh...@nvidia.com>; Chen, > > Xiaoguang <xiaoguang.c...@intel.com>; intel-gvt-...@lists.freedesktop.org; > > Lv, Zhiyuan <zhiyuan...@intel.com>; Wang, Zhi A <zhi.a.w...@intel.com>; > > Wang, Zhenyu Z <zhenyu.z.w...@intel.com> > > Subject: Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf > > operations > > > > On Tue, 20 Jun 2017 12:57:36 +0200 > > Gerd Hoffmann <kra...@redhat.com> wrote: > > > > > On Tue, 2017-06-20 at 08:41 +0000, Zhang, Tina wrote: > > > > 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; > > > > }; > > > > > > Looks good to me. > > > > > > > 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; > > > > }; > > > > > > I'm not convinced the flags are a great idea. Whenever dmabufs or a > > > region is used is a static property of the device, not of each > > > individual plane. > > > > > > > > > I think we should have this for userspace to figure: > > > > > > enum vfio_device_gfx_type { > > > VFIO_DEVICE_GFX_NONE, > > > VFIO_DEVICE_GFX_DMABUF, > > > VFIO_DEVICE_GFX_REGION, > > > }; > > > > > > struct vfio_device_gfx_query_caps { > > > __u32 argsz; > > > __u32 flags; > > > enum vfio_device_gfx_type; > > > }; > > > > We already have VFIO_DEVICE_GET_INFO which returns: > > > > struct vfio_device_info { > > __u32 argsz; > > __u32 flags; > > #define VFIO_DEVICE_FLAGS_RESET (1 << 0) /* Device supports reset */ > > #define VFIO_DEVICE_FLAGS_PCI (1 << 1) /* vfio-pci device */ > > #define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2) /* vfio-platform device */ > > #define VFIO_DEVICE_FLAGS_AMBA (1 << 3) /* vfio-amba device */ > > #define VFIO_DEVICE_FLAGS_CCW (1 << 4) /* vfio-ccw device */ > > __u32 num_regions; /* Max region index + 1 */ > > __u32 num_irqs; /* Max IRQ index + 1 */ > > }; > > > > We could use two flag bits to indicate dmabuf or graphics region support. > > vfio_device_gfx_query_caps seems to imply a new ioctl, which would be > > unnecessary. > > > > > Then this to query the plane: > > > > > > struct vfio_device_gfx_query_plane { > > > __u32 argsz; > > > __u32 flags; > > > struct vfio_device_gfx_plane_info plane_info; /* out */ > > > __u32 plane_type; /* in */ > > > }; > > > > I'm not sure why we're using an enum for something that can currently be > > defined with 2 bits, seems like this would be another good use of flags. We > > could even embed an enum into the flags if we want to leave some expansion > > room, 4 bits maybe? Also, I was imagining that a device could support > > multiple > > graphics regions, that's where specifying the "id" as a region index seemed > > useful. We lose that ability here unless we go back to defining a flag bit > > to > > specify how to interpret this last field. > > > > > 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. > > > > > > Yes. > > > > > > > VFIO_DEVICE_GET_DMABUF_FD: used to create and return the dmabuf fd. > > > > I'm not convinced this adds value, but I'll list it as an option: > > > > VFIO_DEVICE_QUERY(VFIO_DEVICE_GFX_PLANE) > > VFIO_DEVICE_GET_FD(VFIO_DEVICE_GFX_DMABUF_FD) > > > > The benefit is that it might help to avoid a proliferation of ioctls on the > > device the > > pain is that we need to either define a field or section of flags which > > identify > > what is being queried or what type of device fd is being requested. > I didn't understand here. The patch introduces three ioctl commands: > VFIO_DEVICE_GET_FD, VFIO_DMABUF_MGR_QUERY_PLANE, > VFIO_DMABUF_MGR_CREATE_DMABUF. > What I mean was we could remove the first one, a.k.a VFIO_DEVICE_GET_FD, > which is used to get the fd of dmabuf mgr, as we want to remove the logic of > dmabuf mgr. For the other two ioctls, I think we can give them new names > which looks like more general. > So, do you mean there is another way instead of ioctls? Thanks. In this v9 series, we have a VFIO_DEVICE_GET_FD where we could pass VFIO_DEVICE_DMABUF_MGR_FD to get the manager fd, from that fd we could query plane info or get a dmabuf fd. Now we're getting rid of the manager fd and I'm questioning whether generic ioctls or specific ioctls are the right path. For instance we could still use a VFIO_DEVICE_GET_FD ioctl to get the dmabuf fd rather than creating a VFIO_DEVICE_GET_DMABUF_FD ioctl. It's just a matter of defining a common header on the data structure so that we know how to interpret the remainder of the structure. Likewise Gerd proposes above a VFIO_DEVICE_QUERY_GFX_PLANE ioctl and I'm asking whether a generic VFIO_DEVICE_QUERY ioctl where we define a common header in the structure to know that the query is for graphics plane information has value. IOW, should we spend a little bit of time now crafting ioctls that we can use for purposes beyond what we're looking at today, or do we burn off a couple for singular uses here? Thanks, Alex > > > Yes. The plane might have changed between query-plane and get-dmabuf > > > ioctl calls though, we must make sure we handle that somehow. Current > > > patches return plane_info on get-dmabuf ioctl too, so userspace can > > > see what it actually got. > > > > > > With the generation we can also do something different: Pass in > > > plane_type and generation, and have VFIO_DEVICE_GET_DMABUF_FD return > > > an error in case the generation doesn't match. In that case it > > > doesn't make much sense any more to have a separate plane_info struct, > > > which was added so we don't have to duplicate things in query-plane > > > and get- dmabuf ioctl structs. > > > > I'm not sure I understand how this works for a region, the region is always > > the > > current generation, how can the user ever be sure the plane_info matches > > what > > is exposed in the region? Thanks, > > > > Alex _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
