On 7 August 2018 at 13:28, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Tue, Aug 07, 2018 at 12:01:50PM +0100, Emil Velikov wrote: >> On 3 August 2018 at 20:50, Sean Paul <seanpaul@xxxxxxxxxxxx> wrote: >> > On Fri, Aug 03, 2018 at 06:03:50PM +0100, Emil Velikov wrote: >> >> On 3 August 2018 at 16:06, Martin Fuzzey <martin.fuzzey@flowbird.group> wrote: >> >> > Hi Emil, >> >> > >> >> > On 03/08/18 14:35, Emil Velikov wrote: >> >> >> >> >> >> Hi Martin, >> >> >> >> >> >> On 1 August 2018 at 15:24, Martin Fuzzey <martin.fuzzey@flowbird.group> >> >> >> wrote: >> >> >> >> >> >> Let's start with the not-so obvious question: >> >> >> Why does one open the imx as render node? >> >> >> >> >> >> Of the top of my head: >> >> >> There is nothing in egl/android that should require an authenticated >> >> >> device. >> >> >> Hence, using a card node should be fine - the etnaviv code opens the >> >> >> render node it needs. >> >> > >> >> > >> >> > Yes, the problem is not in egl/android but in the scanout buffer allocation >> >> > code. >> >> > >> >> > etnaviv opens the render node on the *GPU* (for submitting GPU commands), >> >> > that part is fine. >> >> > >> >> > But scanout buffers need to be allocated from imx-drm not etnaviv. >> >> > >> >> > This done by renderonly_create_kms_dumb_buffer_for_resource() >> >> > [src/gallium/auxiliary/renderonly/renderonly.c] >> >> > Which uses DRM_IOCTL_MODE_CREATE_DUMB followed by >> >> > DRM_IOCTL_PRIME_FD_TO_HANDLE >> >> > on the "kms_fd" (probably poorly named because it's not actually used for >> >> > modesetting) >> >> > see imx_drm_screen_create()[ src/gallium/winsys/imx/drm/imx_drm_winsys.c] >> >> > >> >> > >> >> > If the card node is used DRM_IOCTL_MODE_CREATE_DUMB works but >> >> > DRM_IOCTL_PRIME_FD_TO_HANDLE fails, because the permissions are >> >> > DRM_AUTH|DRM_UNLOCKED|DRM_RENDER_ALLOW >> >> > >> >> Right I missed the DRM_AUTH, in the fd <> handle IOCTLs. >> >> So in order for things to work, we'd need to either: >> >> - allow dumb buffers for render nodes, or >> >> - drop the DRM_AUTH for fd <> handle imports >> >> >> >> Pointing an alternative solution, for kernel developers to analyse and >> >> make a decision. >> >> >> >> > >> >> > In android 8.1 the hardware composer runs in a seperate process and it has >> >> > to use the card node and be drm master (to use the KMS API), >> >> > therefore, when the surface flinger calls >> >> > renderonly_create_kms_dumb_buffer_for_resource() it is not authenticated. >> >> > >> >> > Making surface flinger use a render node fixes the problem for >> >> > DRM_IOCTL_PRIME_FD_TO_HANDLE (because that already has DRM_RENDER_ALLOW), >> >> > but DRM_IOCTL_MODE_CREATE_DUMB now fails without the patch. >> >> > >> >> > >> >> > This probably worked in previous versions of Android where surface flinger >> >> > and hwc were all in the same process. >> >> > >> >> There has been varying hacks for Android through the years. Bringing >> >> details into the discussion will result in a significant diversion. >> >> Something we could avoid, for the time being ;-) >> > >> > Did someone say diversion?!? The way this was handled prior to using >> > render/control nodes in drm_hwc/[drm/gbm]_gralloc is that all modesetting was >> > done via gralloc which was master. The hwc implementation was basically a proxy >> > backchanneling all of the work to gralloc. >> > >> > Anyways, we probably don't want to go back there. >> > >> Now that we got the diversion out of the way, any input on my proposal >> to drop the DRM_AUTH for fd <> imports. >> Am I missing something pretty obvious that makes the idea a no-go? > > Dropping DRM_AUTH is only relevant for the card node. And a card node > might not be sufficiently isolated against concurrent other clients, which > is why we don't allow it. > Right. I did not spot anything that would make a distinction based on the card vs render node used. > What we could do is essentially check whether your driver supports render > nodes (indicating sufficient amounts of separation), and then allow > anything for unauthenicated clients if DRM_RENDER_ALLOW is set on the > ioctl. > > But that's just reinventing render nodes on top of legacy card nodes, and > I'm not clear on what that exactly gains us. > As more of a userspace person, it makes sense to keep render nodes for GPU specifics and card ones - KMS/Display Controller. > I think the proposal for dumb render nodes (for drivers which only do dumb > kms buffers and no rendering at all) that's been discusson on irc a bit > makes a lot more sense. Ack. Thanks for shedding some light. -Emil _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
