On Tue, Jul 15, 2014 at 05:53:32PM +0000, Bridgman, John wrote: > >From: Jerome Glisse [mailto:j.glisse@xxxxxxxxx] > >Sent: Tuesday, July 15, 2014 1:37 PM > >To: Bridgman, John > >Cc: Dave Airlie; Christian König; Lewycky, Andrew; linux- > >kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Deucher, > >Alexander; akpm@xxxxxxxxxxxxxxxxxxxx > >Subject: Re: [PATCH 00/83] AMD HSA kernel driver > > > >On Tue, Jul 15, 2014 at 05:06:56PM +0000, Bridgman, John wrote: > >> >From: Dave Airlie [mailto:airlied@xxxxxxxxx] > >> >Sent: Tuesday, July 15, 2014 12:35 AM > >> >To: Christian König > >> >Cc: Jerome Glisse; Bridgman, John; Lewycky, Andrew; linux- > >> >kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Deucher, > >> >Alexander; akpm@xxxxxxxxxxxxxxxxxxxx > >> >Subject: Re: [PATCH 00/83] AMD HSA kernel driver > >> > > >> >On 14 July 2014 18:37, Christian König <deathsimple@xxxxxxxxxxx> wrote: > >> >>> I vote for HSA module that expose ioctl and is an intermediary > >> >>> with the kernel driver that handle the hardware. This gives a > >> >>> single point for HSA hardware and yes this enforce things for any > >> >>> hardware > >> >manufacturer. > >> >>> I am more than happy to tell them that this is it and nothing else > >> >>> if they want to get upstream. > >> >> > >> >> I think we should still discuss this single point of entry a bit more. > >> >> > >> >> Just to make it clear the plan is to expose all physical HSA > >> >> capable devices through a single /dev/hsa device node to userspace. > >> > > >> >This is why we don't design kernel interfaces in secret foundations, > >> >and expect anyone to like them. > >> > >> Understood and agree. In this case though this isn't a cross-vendor > >> interface designed by a secret committee, it's supposed to be more of > >> an inoffensive little single-vendor interface designed *for* a secret > >> committee. I'm hoping that's better ;) > >> > >> > > >> >So before we go any further, how is this stuff planned to work for > >> >multiple GPUs/accelerators? > >> > >> Three classes of "multiple" : > >> > >> 1. Single CPU with IOMMUv2 and multiple GPUs: > >> > >> - all devices accessible via /dev/kfd > >> - topology information identifies CPU + GPUs, each has "node ID" at > >> top of userspace API, "global ID" at user/kernel interface (don't > >> think we've implemented CPU part yet though) > >> - userspace builds snapshot from sysfs info & exposes to HSAIL > >> runtime, which in turn exposes the "standard" API > > > >This is why i do not like the sysfs approach, it would be lot nicer to have > >device file per provider and thus hsail can listen on device file event and > >discover if hardware is vanishing or appearing. Periodicaly going over sysfs > >files is not the right way to do that. > > Agree that wouldn't be good. There's an event mechanism still to come - mostly > for communicating fences and shader interrupts back to userspace, but also used > for "device change" notifications, so no polling of sysfs. > My point being, do not use sysfs, use /dev/hsa/device* and have hsail listen on file event on /dev/hsa/ directory. The hsail would be inform of new device and of device that are unloaded. It would do a first pass to open each device file and get there capabilities through standardize ioctl. Thought maybe sysfs is ok given than cpu numa is expose through sysfs > > > >> - kfd sets up ATC aperture so GPUs can access system RAM via IOMMUv2 > >> (fast for APU, relatively less so for dGPU over PCIE) > >> - to-be-added memory operations allow allocation & residency control > >> (within existing gfx driver limits) of buffers in VRAM & carved-out > >> system RAM > >> - queue operations specify a node ID to userspace library, which > >> translates to "global ID" before calling kfd > >> > >> 2. Multiple CPUs connected via fabric (eg HyperTransport) each with 0 or > >more GPUs: > >> > >> - topology information exposes CPUs & GPUs, along with affinity info > >> showing what is connected to what > >> - everything else works as in (1) above > >> > > > >This is suppose to be part of HSA ? This is lot broader than i thought. > > Yes although it can be skipped on most systems. We figured that topology > needed to cover everything that would be handled by a single OS image, so > in a NUMA system it would need to cover all the CPUs. I think that is still > the right scope, do you agree ? I think it is a idea to duplicate cpu. I would rather have each device give its afinity against each cpu and for cpu just keep the existing kernel api that expose this through sysfs iirc. > > > > >> 3. Multiple CPUs not connected via fabric (eg a blade server) each > >> with 0 or more GPUs > >> > >> - no attempt to cover this with HSA topology, each CPU and associated > >> GPUs is accessed independently via separate /dev/kfd instances > >> > >> > > >> >Do we have a userspace to exercise this interface so we can see how > >> >such a thing would look? > >> > >> Yes -- initial IP review done, legal stuff done, sanitizing WIP, > >> hoping for final approval this week > >> > >> There's a separate test harness to exercise the userspace lib calls, > >> haven't started IP review or sanitizing for that but legal stuff is > >> done > >> > >> > > >> >Dave. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
