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

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On 1/20/21 10:59 AM, Daniel Vetter wrote:
On Wed, Jan 20, 2021 at 3:20 PM Andrey Grodzovsky
<Andrey.Grodzovsky@xxxxxxx> 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@xxxxxxx> 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%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072067767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=fjgP9YubHCrILFxWmpVGSmurTJHkWw%2Bv4okyjSNsPxE%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%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072067767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=11PYyAhOjLDEiNNho8WaMB%2FLkA5AuxK6g9XpbNiPIec%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%7Cf3fc3c7b55df40e165f408d8bd5c7364%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637467552072077759%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=q%2F%2FXDKm9LOgw9mq4Ts4JoHR8Ysd8KmoM0NGLD98MsFw%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 ?

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



>From af658ef6b7e5b044d2566104137ee1cb34e52c59 Mon Sep 17 00:00:00 2001
From: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
Date: Mon, 8 Feb 2021 00:41:28 -0500
Subject: DAFT: Add amdgpu command submission while unplug.

---
 tests/core_hotunplug.c | 218 ++++++++++++++++++++++++++++++++++++++++++++++++-
 tests/meson.build      |   2 +-
 2 files changed, 216 insertions(+), 4 deletions(-)

diff --git a/tests/core_hotunplug.c b/tests/core_hotunplug.c
index e7d2a44..5a4dcb4 100644
--- a/tests/core_hotunplug.c
+++ b/tests/core_hotunplug.c
@@ -52,6 +52,190 @@ struct hotunplug {
 	bool need_healthcheck;
 };
 
+/* amdgpu specific code */
+
+#include <amdgpu.h>
+#include <amdgpu_drm.h>
+#include <pthread.h>
+
+#define GFX_COMPUTE_NOP  0xffff1000
+
+
+static bool do_cs;
+
+static int
+amdgpu_bo_alloc_and_map(amdgpu_device_handle dev, unsigned size,
+			unsigned alignment, unsigned heap, uint64_t flags,
+			amdgpu_bo_handle *bo, void **cpu, uint64_t *mc_address,
+			amdgpu_va_handle *va_handle)
+{
+	struct amdgpu_bo_alloc_request request = {
+		.alloc_size = size,
+		.phys_alignment = alignment,
+		.preferred_heap = heap,
+		.flags = flags,
+	};
+	amdgpu_bo_handle buf_handle;
+	amdgpu_va_handle handle;
+	uint64_t vmc_addr;
+	int r;
+
+	r = amdgpu_bo_alloc(dev, &request, &buf_handle);
+	if (r)
+		return r;
+
+	r = amdgpu_va_range_alloc(dev,
+				  amdgpu_gpu_va_range_general,
+				  size, alignment, 0, &vmc_addr,
+				  &handle, 0);
+	if (r)
+		goto error_va_alloc;
+
+	r = amdgpu_bo_va_op(buf_handle, 0, size, vmc_addr, 0, AMDGPU_VA_OP_MAP);
+	if (r)
+		goto error_va_map;
+
+	r = amdgpu_bo_cpu_map(buf_handle, cpu);
+	if (r)
+		goto error_cpu_map;
+
+	*bo = buf_handle;
+	*mc_address = vmc_addr;
+	*va_handle = handle;
+
+	return 0;
+
+error_cpu_map:
+	amdgpu_bo_cpu_unmap(buf_handle);
+
+error_va_map:
+	amdgpu_bo_va_op(buf_handle, 0, size, vmc_addr, 0, AMDGPU_VA_OP_UNMAP);
+
+error_va_alloc:
+	amdgpu_bo_free(buf_handle);
+	return r;
+}
+
+static void
+amdgpu_bo_unmap_and_free(amdgpu_bo_handle bo, amdgpu_va_handle va_handle,
+			 uint64_t mc_addr, uint64_t size)
+{
+	amdgpu_bo_cpu_unmap(bo);
+	amdgpu_bo_va_op(bo, 0, size, mc_addr, 0, AMDGPU_VA_OP_UNMAP);
+	amdgpu_va_range_free(va_handle);
+	amdgpu_bo_free(bo);
+}
+
+static void amdgpu_cs_sync(amdgpu_context_handle context,
+			   unsigned int ip_type,
+			   int ring,
+			   unsigned int seqno)
+{
+	struct amdgpu_cs_fence fence = {
+		.context = context,
+		.ip_type = ip_type,
+		.ring = ring,
+		.fence = seqno,
+	};
+	uint32_t expired;
+	int err;
+
+	err = amdgpu_cs_query_fence_status(&fence,
+					   AMDGPU_TIMEOUT_INFINITE,
+					   0, &expired);
+}
+
+static void *amdgpu_nop_cs(void *p)
+{
+	int fd = *(int *)p;
+	amdgpu_bo_handle ib_result_handle;
+	void *ib_result_cpu;
+	uint64_t ib_result_mc_address;
+	uint32_t *ptr;
+	int i, r;
+	amdgpu_bo_list_handle bo_list;
+	amdgpu_va_handle va_handle;
+	uint32_t major, minor;
+	amdgpu_device_handle device;
+	amdgpu_context_handle context;
+	struct amdgpu_cs_request ibs_request;
+	struct amdgpu_cs_ib_info ib_info;
+
+
+	r = amdgpu_device_initialize(fd, &major, &minor, &device);
+	igt_require(r == 0);
+
+	r = amdgpu_cs_ctx_create(device, &context);
+	igt_assert_eq(r, 0);
+
+	r = amdgpu_bo_alloc_and_map(device, 4096, 4096,
+				    AMDGPU_GEM_DOMAIN_GTT, 0,
+				    &ib_result_handle, &ib_result_cpu,
+				    &ib_result_mc_address, &va_handle);
+	igt_assert_eq(r, 0);
+
+	ptr = ib_result_cpu;
+	for (i = 0; i < 16; ++i)
+		ptr[i] = GFX_COMPUTE_NOP;
+
+	r = amdgpu_bo_list_create(device, 1, &ib_result_handle, NULL, &bo_list);
+	igt_assert_eq(r, 0);
+
+	memset(&ib_info, 0, sizeof(struct amdgpu_cs_ib_info));
+	ib_info.ib_mc_address = ib_result_mc_address;
+	ib_info.size = 16;
+
+	memset(&ibs_request, 0, sizeof(struct amdgpu_cs_request));
+	ibs_request.ip_type = AMDGPU_HW_IP_GFX;
+	ibs_request.ring = 0;
+	ibs_request.number_of_ibs = 1;
+	ibs_request.ibs = &ib_info;
+	ibs_request.resources = bo_list;
+
+	while (do_cs)
+		amdgpu_cs_submit(context, 0, &ibs_request, 1);
+
+	amdgpu_cs_sync(context, AMDGPU_HW_IP_GFX, 0, ibs_request.seq_no);
+
+	amdgpu_bo_list_destroy(bo_list);
+
+	amdgpu_bo_unmap_and_free(ib_result_handle, va_handle,
+				 ib_result_mc_address, 4096);
+
+	amdgpu_cs_ctx_free(context);
+	amdgpu_device_deinitialize(device);
+
+	return (void *)0;
+}
+
+static pthread_t* amdgpu_create_cs_thread(int *fd)
+{
+	int r;
+	pthread_t *thread = malloc(sizeof(*thread));
+
+	do_cs = true;
+
+	r = pthread_create(thread, NULL, amdgpu_nop_cs, (void *)fd);
+	igt_assert_eq(r, 0);
+
+	/* Give thread enough time to start*/
+	usleep(100000);
+	return thread;
+}
+
+static void amdgpu_destroy_cs_thread(pthread_t *thread)
+{
+	void *status;
+
+	do_cs = false;
+
+	pthread_join(*thread, &status);
+	igt_assert(status == 0);
+
+	free(thread);
+}
+
+

@@ -455,15 +645,26 @@ static void unplug_rescan(struct hotunplug *priv)
 
 static void hotunbind_rebind(struct hotunplug *priv)
 {
+	pthread_t *thread = NULL;
+
 	pre_check(priv);
 
 	priv->fd.drm = local_drm_open_driver(false, "", " for hot unbind");
 
+	if (is_amdgpu_device(priv->fd.drm))
+		thread = amdgpu_create_cs_thread(&priv->fd.drm);
+
 	driver_unbind(priv, "hot ", 0);
 
+	if (thread)
+		amdgpu_destroy_cs_thread(thread);
+
+
 	priv->fd.drm = close_device(priv->fd.drm, "late ", "unbound ");
 	igt_assert_eq(priv->fd.drm, -1);
 
 	driver_bind(priv, 0);
 
 	igt_assert_f(healthcheck(priv, false), "%s\n", priv->failure);
@@ -471,15 +672,25 @@ static void hotunbind_rebind(struct hotunplug *priv)
 
 static void hotunplug_rescan(struct hotunplug *priv)
 {
+	pthread_t *thread = NULL;
+
 	pre_check(priv);
 
 	priv->fd.drm = local_drm_open_driver(false, "", " for hot unplug");
 
+	if (is_amdgpu_device(priv->fd.drm))
+		thread = amdgpu_create_cs_thread(&priv->fd.drm);
+
 	device_unplug(priv, "hot ", 0);
 
+	if (thread)
+		amdgpu_destroy_cs_thread(thread);
+
 	priv->fd.drm = close_device(priv->fd.drm, "late ", "removed ");
 	igt_assert_eq(priv->fd.drm, -1);

 	bus_rescan(priv, 0);
 
 	igt_assert_f(healthcheck(priv, false), "%s\n", priv->failure);
@@ -543,6 +754,7 @@ static void hotreplug_lateclose(struct hotunplug *priv)
 	igt_assert_f(healthcheck(priv, false), "%s\n", priv->failure);
 }
 
diff --git a/tests/meson.build b/tests/meson.build
index 825e018..1de6cc5 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -243,7 +243,7 @@ i915_progs = [
 	'sysfs_timeslice_duration',
 ]
 
-test_deps = [ igt_deps ]
+test_deps = [ igt_deps + [ libdrm_amdgpu ] ]
 
 if libdrm_nouveau.found()
 	test_progs += [
-- 
2.7.4

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