Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752619AbdFTXWK (ORCPT ); Tue, 20 Jun 2017 19:22:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41606 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbdFTXWJ (ORCPT ); Tue, 20 Jun 2017 19:22:09 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com CDB484E4C3 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=alex.williamson@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com CDB484E4C3 Date: Tue, 20 Jun 2017 17:22:04 -0600 From: Alex Williamson To: "Zhang, Tina" Cc: Gerd Hoffmann , "intel-gfx@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , Kirti Wankhede , "Chen, Xiaoguang" , "intel-gvt-dev@lists.freedesktop.org" , "Lv, Zhiyuan" , "Wang, Zhi A" , "Wang, Zhenyu Z" Subject: Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations Message-ID: <20170620172204.09405cf4@w520.home> In-Reply-To: <237F54289DF84E4997F34151298ABEBC7C56F3DC@SHSMSX101.ccr.corp.intel.com> References: <1497513611-2814-1-git-send-email-xiaoguang.chen@intel.com> <1497513611-2814-6-git-send-email-xiaoguang.chen@intel.com> <1497542438.29252.1.camel@redhat.com> <20170615143833.7526351b@w520.home> <24c4880b-24f5-ea07-834c-c77d3e895c78@nvidia.com> <1497854312.4207.4.camel@redhat.com> <20170619085530.1f5e46dc@w520.home> <237F54289DF84E4997F34151298ABEBC7C56EBE0@SHSMSX101.ccr.corp.intel.com> <1497956256.16795.7.camel@redhat.com> <20170620090004.44ac7fbc@w520.home> <237F54289DF84E4997F34151298ABEBC7C56F3DC@SHSMSX101.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 20 Jun 2017 23:22:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6968 Lines: 163 On Tue, 20 Jun 2017 23:01:53 +0000 "Zhang, Tina" wrote: > > -----Original Message----- > > From: Alex Williamson [mailto:alex.williamson@redhat.com] > > Sent: Tuesday, June 20, 2017 11:00 PM > > To: Gerd Hoffmann > > Cc: Zhang, Tina ; intel-gfx@lists.freedesktop.org; linux- > > kernel@vger.kernel.org; Kirti Wankhede ; Chen, > > Xiaoguang ; intel-gvt-dev@lists.freedesktop.org; > > Lv, Zhiyuan ; Wang, Zhi A ; > > Wang, Zhenyu Z > > 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 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