[PATCH v4 00/14] RFC Support hot device unplug in amdgpu
Daniel Vetter
daniel at ffwll.ch
Mon Feb 8 07:27:13 UTC 2021
On Mon, Feb 8, 2021 at 6:59 AM Andrey Grodzovsky
<Andrey.Grodzovsky at amd.com> wrote:
>
>
> On 1/20/21 10:59 AM, Daniel Vetter wrote:
> > On Wed, Jan 20, 2021 at 3:20 PM Andrey Grodzovsky
> > <Andrey.Grodzovsky at amd.com> wrote:
> >>
> >> On 1/20/21 4:05 AM, Daniel Vetter wrote:
> >>> On Tue, Jan 19, 2021 at 01:18:15PM -0500, Andrey Grodzovsky wrote:
> >>>> On 1/19/21 1:08 PM, Daniel Vetter wrote:
> >>>>> On Tue, Jan 19, 2021 at 6:31 PM Andrey Grodzovsky
> >>>>> <Andrey.Grodzovsky at amd.com> wrote:
> >>>>>> On 1/19/21 9:16 AM, Daniel Vetter wrote:
> >>>>>>> On Mon, Jan 18, 2021 at 04:01:09PM -0500, Andrey Grodzovsky wrote:
> >>>>>>>> Until now extracting a card either by physical extraction (e.g. eGPU with
> >>>>>>>> thunderbolt connection or by emulation through syfs -> /sys/bus/pci/devices/device_id/remove)
> >>>>>>>> would cause random crashes in user apps. The random crashes in apps were
> >>>>>>>> mostly due to the app having mapped a device backed BO into its address
> >>>>>>>> space was still trying to access the BO while the backing device was gone.
> >>>>>>>> To answer this first problem Christian suggested to fix the handling of mapped
> >>>>>>>> memory in the clients when the device goes away by forcibly unmap all buffers the
> >>>>>>>> user processes has by clearing their respective VMAs mapping the device BOs.
> >>>>>>>> Then when the VMAs try to fill in the page tables again we check in the fault
> >>>>>>>> handlerif the device is removed and if so, return an error. This will generate a
> >>>>>>>> SIGBUS to the application which can then cleanly terminate.This indeed was done
> >>>>>>>> but this in turn created a problem of kernel OOPs were the OOPSes were due to the
> >>>>>>>> fact that while the app was terminating because of the SIGBUSit would trigger use
> >>>>>>>> after free in the driver by calling to accesses device structures that were already
> >>>>>>>> released from the pci remove sequence.This was handled by introducing a 'flush'
> >>>>>>>> sequence during device removal were we wait for drm file reference to drop to 0
> >>>>>>>> meaning all user clients directly using this device terminated.
> >>>>>>>>
> >>>>>>>> v2:
> >>>>>>>> Based on discussions in the mailing list with Daniel and Pekka [1] and based on the document
> >>>>>>>> produced by Pekka from those discussions [2] the whole approach with returning SIGBUS and
> >>>>>>>> waiting for all user clients having CPU mapping of device BOs to die was dropped.
> >>>>>>>> Instead as per the document suggestion the device structures are kept alive until
> >>>>>>>> the last reference to the device is dropped by user client and in the meanwhile all existing and new CPU mappings of the BOs
> >>>>>>>> belonging to the device directly or by dma-buf import are rerouted to per user
> >>>>>>>> process dummy rw page.Also, I skipped the 'Requirements for KMS UAPI' section of [2]
> >>>>>>>> since i am trying to get the minimal set of requirements that still give useful solution
> >>>>>>>> to work and this is the'Requirements for Render and Cross-Device UAPI' section and so my
> >>>>>>>> test case is removing a secondary device, which is render only and is not involved
> >>>>>>>> in KMS.
> >>>>>>>>
> >>>>>>>> v3:
> >>>>>>>> More updates following comments from v2 such as removing loop to find DRM file when rerouting
> >>>>>>>> page faults to dummy page,getting rid of unnecessary sysfs handling refactoring and moving
> >>>>>>>> prevention of GPU recovery post device unplug from amdgpu to scheduler layer.
> >>>>>>>> On top of that added unplug support for the IOMMU enabled system.
> >>>>>>>>
> >>>>>>>> v4:
> >>>>>>>> Drop last sysfs hack and use sysfs default attribute.
> >>>>>>>> Guard against write accesses after device removal to avoid modifying released memory.
> >>>>>>>> Update dummy pages handling to on demand allocation and release through drm managed framework.
> >>>>>>>> Add return value to scheduler job TO handler (by Luben Tuikov) and use this in amdgpu for prevention
> >>>>>>>> of GPU recovery post device unplug
> >>>>>>>> Also rebase on top of drm-misc-mext instead of amd-staging-drm-next
> >>>>>>>>
> >>>>>>>> With these patches I am able to gracefully remove the secondary card using sysfs remove hook while glxgears
> >>>>>>>> is running off of secondary card (DRI_PRIME=1) without kernel oopses or hangs and keep working
> >>>>>>>> with the primary card or soft reset the device without hangs or oopses
> >>>>>>>>
> >>>>>>>> TODOs for followup work:
> >>>>>>>> Convert AMDGPU code to use devm (for hw stuff) and drmm (for sw stuff and allocations) (Daniel)
> >>>>>>>> Support plugging the secondary device back after unplug - currently still experiencing HW error on plugging back.
> >>>>>>>> Add support for 'Requirements for KMS UAPI' section of [2] - unplugging primary, display connected card.
> >>>>>>>>
> >>>>>>>> [1] - Discussions during v3 of the patchset https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Famd-gfx%2Fmsg55576.html&data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072067767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=fjgP9YubHCrILFxWmpVGSmurTJHkWw%2Bv4okyjSNsPxE%3D&reserved=0
> >>>>>>>> [2] - drm/doc: device hot-unplug for userspace https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Fdri-devel%2Fmsg259755.html&data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072067767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=11PYyAhOjLDEiNNho8WaMB%2FLkA5AuxK6g9XpbNiPIec%3D&reserved=0
> >>>>>>>> [3] - Related gitlab ticket https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1081&data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072077759%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=q%2F%2FXDKm9LOgw9mq4Ts4JoHR8Ysd8KmoM0NGLD98MsFw%3D&reserved=0
> >>>>>>> btw have you tried this out with some of the igts we have? core_hotunplug
> >>>>>>> is the one I'm thinking of. Might be worth to extend this for amdgpu
> >>>>>>> specific stuff (like run some batches on it while hotunplugging).
> >>>>>> No, I mostly used just running glxgears while testing which covers already
> >>>>>> exported/imported dma-buf case and a few manually hacked tests in libdrm amdgpu
> >>>>>> test suite
> >>>>>>
> >>>>>>
> >>>>>>> Since there's so many corner cases we need to test here (shared dma-buf,
> >>>>>>> shared dma_fence) I think it would make sense to have a shared testcase
> >>>>>>> across drivers.
> >>>>>> Not familiar with IGT too much, is there an easy way to setup shared dma bufs
> >>>>>> and fences
> >>>>>> use cases there or you mean I need to add them now ?
> >>>>> We do have test infrastructure for all of that, but the hotunplug test
> >>>>> doesn't have that yet I think.
> >>>>>
> >>>>>>> Only specific thing would be some hooks to keep the gpu
> >>>>>>> busy in some fashion while we yank the driver.
> >>>>>> Do you mean like staring X and some active rendering on top (like glxgears)
> >>>>>> automatically from within IGT ?
> >>>>> Nope, igt is meant to be bare metal testing so you don't have to drag
> >>>>> the entire winsys around (which in a wayland world, is not really good
> >>>>> for driver testing anyway, since everything is different). We use this
> >>>>> for our pre-merge ci for drm/i915.
> >>>> So i keep it busy by X/glxgers which is manual operation. What you suggest
> >>>> then is some client within IGT which opens the device and starts submitting jobs
> >>>> (which is much like what libdrm amdgpu tests already do) ? And this
> >>>> part is the amdgou specific code I just need to port from libdrm to here ?
> >>> Yup. For i915 tests we have an entire library already for small workloads,
> >>> including some that just spin forever (useful for reset testing and could
> >>> also come handy for unload testing).
> >>> -Daniel
> >>
> >> Does it mean I would have to drag in the entire infrastructure code from
> >> within libdrm amdgpu code that allows for command submissions through
> >> our IOCTLs ?
> > No it's perfectly fine to use libdrm in igt tests, we do that too. I
> > just mean we have some additional helpers to submit specific workloads
> > for intel gpu, like rendercpy to move data with the 3d engine (just
> > using copy engines only isn't good enough sometimes for testing), or
> > the special hanging batchbuffers we use for reset testing, or in
> > general for having precise control over race conditions and things
> > like that.
> >
> > One thing that was somewhat annoying for i915 but shouldn't be a
> > problem for amdgpu is that igt builds on intel. So we have stub
> > functions for libdrm-intel, since libdrm-intel doesn't build on arm.
> > Shouldn't be a problem for you.
> > -Daniel
>
>
> Tested with igt hot-unplug test. Passed unbind_rebind, unplug-rescan,
> hot-unbind-rebind and hotunplug-rescan
> if disabling the rescan part as I don't support plug-back for now. Also added
> command submission for amdgpu.
> Attached a draft of submitting workload while unbinding the driver or simulating
> detach. Catched 2 issues with unpug if command submission in flight during
> unplug -
> (unsignaled fence causing a hang in amdgpu_cs_sync and hitting a BUG_ON in
> gfx_v9_0_ring_emit_patch_cond_exec whic is expected i guess).
> Guess glxgears command submissions is at a much slower rate so this was missed.
> Is that what you meant for this test ?
Yup. Would be good if you can submit this one for inclusion.
-Daniel
>
> Andrey
>
>
> >
> >
> >> Andrey
> >>
> >>>> Andrey
> >>>>
> >>>>
> >>>>>>> But just to get it started
> >>>>>>> you can throw in entirely amdgpu specific subtests and just share some of
> >>>>>>> the test code.
> >>>>>>> -Daniel
> >>>>>> Im general, I wasn't aware of this test suite and looks like it does what i test
> >>>>>> among other stuff.
> >>>>>> I will definitely try to run with it although the rescan part will not work as
> >>>>>> plugging
> >>>>>> the device back is in my TODO list and not part of the scope for this patchset
> >>>>>> and so I will
> >>>>>> probably comment the re-scan section out while testing.
> >>>>> amd gem has been using libdrm-amd thus far iirc, but for things like
> >>>>> this I think it'd be worth to at least consider switching. Display
> >>>>> team has already started to use some of the test and contribute stuff
> >>>>> (I think the VRR testcase is from amd).
> >>>>> -Daniel
> >>>>>
> >>>>>> Andrey
> >>>>>>
> >>>>>>
> >>>>>>>> Andrey Grodzovsky (13):
> >>>>>>>> drm/ttm: Remap all page faults to per process dummy page.
> >>>>>>>> drm: Unamp the entire device address space on device unplug
> >>>>>>>> drm/ttm: Expose ttm_tt_unpopulate for driver use
> >>>>>>>> drm/sched: Cancel and flush all oustatdning jobs before finish.
> >>>>>>>> drm/amdgpu: Split amdgpu_device_fini into early and late
> >>>>>>>> drm/amdgpu: Add early fini callback
> >>>>>>>> drm/amdgpu: Register IOMMU topology notifier per device.
> >>>>>>>> drm/amdgpu: Fix a bunch of sdma code crash post device unplug
> >>>>>>>> drm/amdgpu: Remap all page faults to per process dummy page.
> >>>>>>>> dmr/amdgpu: Move some sysfs attrs creation to default_attr
> >>>>>>>> drm/amdgpu: Guard against write accesses after device removal
> >>>>>>>> drm/sched: Make timeout timer rearm conditional.
> >>>>>>>> drm/amdgpu: Prevent any job recoveries after device is unplugged.
> >>>>>>>>
> >>>>>>>> Luben Tuikov (1):
> >>>>>>>> drm/scheduler: Job timeout handler returns status
> >>>>>>>>
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 11 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 17 +--
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 149 ++++++++++++++++++++--
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 20 ++-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 15 ++-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_gart.h | 1 +
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 9 ++
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c | 25 ++--
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c | 26 ++--
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_irq.h | 3 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 19 ++-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 12 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 10 ++
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 2 +
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c | 53 +++++---
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_psp.h | 3 +
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c | 1 +
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c | 70 ++++++++++
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 52 +-------
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 21 ++-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 8 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 14 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/cik_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/cz_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/iceland_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/navi10_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/psp_v11_0.c | 16 +--
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/psp_v12_0.c | 8 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/psp_v3_1.c | 8 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/si_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/tonga_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/amdgpu/vega10_ih.c | 2 +-
> >>>>>>>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 +-
> >>>>>>>> drivers/gpu/drm/amd/include/amd_shared.h | 2 +
> >>>>>>>> drivers/gpu/drm/drm_drv.c | 3 +
> >>>>>>>> drivers/gpu/drm/etnaviv/etnaviv_sched.c | 10 +-
> >>>>>>>> drivers/gpu/drm/lima/lima_sched.c | 4 +-
> >>>>>>>> drivers/gpu/drm/panfrost/panfrost_job.c | 9 +-
> >>>>>>>> drivers/gpu/drm/scheduler/sched_main.c | 18 ++-
> >>>>>>>> drivers/gpu/drm/ttm/ttm_bo_vm.c | 82 +++++++++++-
> >>>>>>>> drivers/gpu/drm/ttm/ttm_tt.c | 1 +
> >>>>>>>> drivers/gpu/drm/v3d/v3d_sched.c | 32 ++---
> >>>>>>>> include/drm/gpu_scheduler.h | 17 ++-
> >>>>>>>> include/drm/ttm/ttm_bo_api.h | 2 +
> >>>>>>>> 45 files changed, 583 insertions(+), 198 deletions(-)
> >>>>>>>>
> >>>>>>>> --
> >>>>>>>> 2.7.4
> >>>>>>>>
> >
> >
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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