Re: [PATCH v4 00/14] RFC Support hot device unplug in amdgpu

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Feb 08, 2021 at 11:01:14PM -0500, Andrey Grodzovsky wrote:
> 
> On 2/8/21 2:27 AM, Daniel Vetter wrote:
> > On Mon, Feb 8, 2021 at 6:59 AM Andrey Grodzovsky
> > <Andrey.Grodzovsky@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@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@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&amp;data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cec5a382fde9d43c0397408d8cc02fc38%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637483660504372326%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=5AtLTzLpQ05h1ZonovShf5TUYwOTywkV1WJ1pXfB%2BCA%3D&amp;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&amp;data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cec5a382fde9d43c0397408d8cc02fc38%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637483660504372326%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=zCBMxQnSeiuFORHHxlSpx10v4gwZ%2BnbTFnxelmWliJo%3D&amp;reserved=0
> > > > > > > > > > > [3] - Related gitlab ticket https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1081&amp;data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7Cec5a382fde9d43c0397408d8cc02fc38%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637483660504372326%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=d9rifeYMoPcbE8K5axZvnSy2kQ3ENWgUcpvol6TkkMw%3D&amp;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
> 
> 
> Will do together with exported dma-buf test once I do it.
> 
> P.S How am i supposed to do exported fence test. Exporting a fence from
> device A, importing it into device B, unplugging
> device A then signaling the fence from device B - this supposed to call a
> fence cb which was registered
> by the exporter which by now is dead and hence will cause a 'use after free' ?

Yeah in the end we'd need 2 hw devices for testing full fence
functionality. A useful intermediate step would be to just export the
fence (either as sync_file, which I think amdgpu doesn't support because
no android egl support in mesa) or drm_syncobj (which you can do as
standalone fd too iirc), and then just using the fence a bit from
userspace (like wait on it or get its status) after the device is
unplugged.

I think this should cover most of the cross-driver issues that fences
bring in, and I think for the other problems we can worry once we spot.
-Daniel

> 
> Andrey
> 
> > 
> > > 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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