Re: [PATCH] drm/amdgpu: avoid clearing freed bo with sdma in gpu reset

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Yes, exactly that one.

Regards,
Christian.

Am 06.05.20 um 12:35 schrieb Zhou, Tiecheng:
[AMD Official Use Only - Internal Distribution Only]

Thanks, Christian,

Is this the fix that you are mentioning:

commit 1675c3a24d075d484377003789245f48c2114a0b
Author: Christian König <christian.koenig@xxxxxxx>
Date:   Fri Feb 21 15:10:31 2020 +0100

     drm/amdgpu: stop disable the scheduler during HW fini

     When we stop the HW for example for GPU reset we should not stop the
     front-end scheduler. Otherwise we run into intermediate failures during
     command submission.

     The scheduler should only be stopped in very few cases:
     1. We can't get the hardware working in ring or IB test after a GPU reset.
     2. The KIQ scheduler is not used in the front-end and should be disabled during GPU reset.
     3. In amdgpu_ring_fini() when the driver unloads.

     Signed-off-by: Christian König <christian.koenig@xxxxxxx>
     Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx>
     Acked-by: Nirmoy Das <nirmoy.das@xxxxxxx>
     Test-by: Dennis Li <dennis.li@xxxxxxx>
     Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>

Thanks
Tiecheng


-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Sent: Wednesday, May 6, 2020 5:44 PM
To: Zhou, Tiecheng <Tiecheng.Zhou@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amdgpu: avoid clearing freed bo with sdma in gpu reset

NAK, the fundamental problem was that we disabled the SDMA paging queue during reset:
[  885.694682] [drm] schedpage0 is not ready, skipping [  885.694682]
[drm] schedpage1 is not ready, skipping
This is fixed by now, so the problem should not happen any more.

Regards,
Christian.


Am 06.05.20 um 11:36 schrieb Tiecheng Zhou:
WHY:
For V320 passthrough and "modprobe amdgpu lockup_timeout=500", there
will be kernel NULL pointer when using quark ~ BACO reset, for instance:
    hang_vm_compute0_bad_cs_dispatch.lua
    hang_vm_dma0_corrupted_header.lua
    etc.
-----------------------------
[  884.792885] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring
comp_1.0.0 timeout, signaled seq=3, emitted seq=4 [  884.793772]
[drm:amdgpu_job_timedout [amdgpu]] *ERROR* Process information:
process quark pid 16939 thread quark pid 16940 [  884.859979] amdgpu:
[powerplay] set virtualization GFX DPM policy success [  884.861003]
amdgpu: [powerplay] activate virtualization GFX DPM policy success [  884.861065] amdgpu: [powerplay] set virtualization VCE DPM policy success [  885.693554] [drm:amdgpu_cs_ioctl [amdgpu]] *ERROR* Failed to initialize parser -125!
[  885.694682] [drm] schedpage0 is not ready, skipping [  885.694682]
[drm] schedpage1 is not ready, skipping [  885.694720]
[drm:amdgpu_gem_va_ioctl [amdgpu]] *ERROR* Couldn't update BO_VA (-2)
[  885.695328] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000008 [  885.695909] PGD 0 P4D 0 [  885.696104] Oops:
0000 [#1] SMP PTI
[  885.696368] CPU: 2 PID: 16940 Comm: quark Tainted: G           OE     4.19.52+ #6
[  885.696945] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1 04/01/2014 [  885.697593] RIP:
0010:amdgpu_vm_sdma_commit+0x59/0x130 [amdgpu] ...
[  885.705042] Call Trace:
[  885.705251]  ? amdgpu_vm_bo_update_mapping+0xdf/0xf0 [amdgpu] [
885.705696]  ? amdgpu_vm_clear_freed+0xcc/0x1b0 [amdgpu] [
885.706112]  ? amdgpu_gem_va_ioctl+0x4a1/0x510 [amdgpu] [  885.706493]
? __radix_tree_delete+0x7e/0xa0 [  885.706822]  ?
amdgpu_gem_va_map_flags+0x70/0x70 [amdgpu] [  885.707220]  ?
drm_ioctl_kernel+0xaa/0xf0 [drm] [  885.707568]  ?
amdgpu_gem_va_map_flags+0x70/0x70 [amdgpu] [  885.707962]  ?
drm_ioctl_kernel+0xaa/0xf0 [drm] [  885.708294]  ?
drm_ioctl+0x3a7/0x3f0 [drm] [  885.708632]  ?
amdgpu_gem_va_map_flags+0x70/0x70 [amdgpu] [  885.709032]  ?
unmap_region+0xd9/0x120 [  885.709328]  ? amdgpu_drm_ioctl+0x49/0x80
[amdgpu] [  885.709684]  ? do_vfs_ioctl+0xa1/0x620 [  885.709971]  ?
do_munmap+0x32e/0x430 [  885.710232]  ? ksys_ioctl+0x66/0x70 [
885.710513]  ? __x64_sys_ioctl+0x16/0x20 [  885.710806]  ?
do_syscall_64+0x55/0x100 [  885.711092]  ?
entry_SYSCALL_64_after_hwframe+0x44/0xa9
...
[  885.719408] ---[ end trace 7ee3180f42e9f572 ]--- [  885.719766]
RIP: 0010:amdgpu_vm_sdma_commit+0x59/0x130 [amdgpu] ...
-----------------------------

the NULL pointer (entity->rq == NULL in amdgpu_vm_sdma_commit()) as follows:
1. quark sends bad job that triggers job timeout; 2. guest KMD detects
the job timeout and goes to gpu recovery, and it goes to
     ip_suspend for SDMA, and it sets sdma[].sched.ready to false; 3.
quark sends UNMAP operation through amdgpu_gem_va_ioctl, and guest KMD goes
     through amdgpu_gem_va_update_vm and finally goes to amdgpu_vm_sdma_commit,
     it goes to amdgpu_job_submit to drm_sched_job_init 4.
drm_sched_job_init fails at drm_sched_pick_best() since
     sdma[].sched.ready is set to false; in the meanwhile entity->rq
becomes NULL; 5. quark sends other UNMAP operations through amdgpu_gem_va_ioctl, while this time
     there will be NULL pointer because entity->rq is NULL;

the above sequence occurs only when "modprobe amdgpu lockup_timeout=500".
it does not occur when lockup_timeout=10000 (default) because step 2.
KMD detects job timeout will be sometime after quark sends UNMAP
operations; i.e. quark UNMAP opeartions are finished before sdma ip suspend.

HOW:
here is to add mutex_lock to wait to avoid using sdma during gpu reset.

Signed-off-by: Tiecheng Zhou <Tiecheng.Zhou@xxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 ++++
   1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index e205ecc75a21..018b88f3b6da 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2047,6 +2047,8 @@ int amdgpu_vm_clear_freed(struct amdgpu_device *adev,
   	struct dma_fence *f = NULL;
   	int r;
+ mutex_lock(&adev->lock_reset);
+
   	while (!list_empty(&vm->freed)) {
   		mapping = list_first_entry(&vm->freed,
   			struct amdgpu_bo_va_mapping, list); @@ -2062,6 +2064,7 @@ int
amdgpu_vm_clear_freed(struct amdgpu_device *adev,
   		amdgpu_vm_free_mapping(adev, vm, mapping, f);
   		if (r) {
   			dma_fence_put(f);
+			mutex_unlock(&adev->lock_reset);
   			return r;
   		}
   	}
@@ -2073,6 +2076,7 @@ int amdgpu_vm_clear_freed(struct amdgpu_device *adev,
   		dma_fence_put(f);
   	}
+ mutex_unlock(&adev->lock_reset);
   	return 0;
}

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