[AMD Official Use Only - AMD Internal Distribution Only]
Hi Felix,
You are right, it is easily to hit deadlock, don't know why LOCKDEP doesn't catch this. Need to find another solution.
Hi Philip,
Do you have a solution for this delay free pt?
Emily Deng
Best Wishes
>-----Original Message-----
>From: Deng, Emily <Emily.Deng@xxxxxxx>
>Sent: Tuesday, January 7, 2025 10:34 AM
>To: Deng, Emily <Emily.Deng@xxxxxxx>; Kuehling, Felix
><Felix.Kuehling@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; Yang, Philip
><Philip.Yang@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>
>Subject: RE: [PATCH v2] drm/amdgpu: Fix the looply call svm_range_restore_pages
>issue
>
>[AMD Official Use Only - AMD Internal Distribution Only]
>
>Ping....
>How about this? Currently it is easily to reproduce the issue on our environment. We
>need this change to fix it.
>
>Emily Deng
>Best Wishes
>
>
>
>>-----Original Message-----
>>From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>>Deng, Emily
>>Sent: Monday, January 6, 2025 9:52 AM
>>To: Kuehling, Felix <Felix.Kuehling@xxxxxxx>;
>>amd-gfx@xxxxxxxxxxxxxxxxxxxxx; Yang, Philip <Philip.Yang@xxxxxxx>;
>>Koenig, Christian <Christian.Koenig@xxxxxxx>
>>Subject: RE: [PATCH v2] drm/amdgpu: Fix the looply call
>>svm_range_restore_pages issue
>>
>>[AMD Official Use Only - AMD Internal Distribution Only]
>>
>>[AMD Official Use Only - AMD Internal Distribution Only]
>>
>>>-----Original Message-----
>>>From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
>>>Sent: Saturday, January 4, 2025 7:18 AM
>>>To: Deng, Emily <Emily.Deng@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx;
>>>Yang, Philip <Philip.Yang@xxxxxxx>; Koenig, Christian
>>><Christian.Koenig@xxxxxxx>
>>>Subject: Re: [PATCH v2] drm/amdgpu: Fix the looply call
>>>svm_range_restore_pages issue
>>>
>>>
>>>On 2025-01-02 21:26, Emily Deng wrote:
>>>> As the delayed free pt, the wanted freed bo has been reused which
>>>> will cause unexpected page fault, and then call svm_range_restore_pages.
>>>>
>>>> Detail as below:
>>>> 1.It wants to free the pt in follow code, but it is not freed
>>>> immediately and used “schedule_work(&vm->pt_free_work);”.
>>>>
>>>> [ 92.276838] Call Trace:
>>>> [ 92.276841] dump_stack+0x63/0xa0
>>>> [ 92.276887] amdgpu_vm_pt_free_list+0xfb/0x120 [amdgpu]
>>>> [ 92.276932] amdgpu_vm_update_range+0x69c/0x8e0 [amdgpu]
>>>> [ 92.276990] svm_range_unmap_from_gpus+0x112/0x310 [amdgpu]
>>>> [ 92.277046] svm_range_cpu_invalidate_pagetables+0x725/0x780 [amdgpu]
>>>> [ 92.277050] ? __alloc_pages_nodemask+0x19f/0x3e0
>>>> [ 92.277051] mn_itree_invalidate+0x72/0xc0
>>>> [ 92.277052] __mmu_notifier_invalidate_range_start+0x48/0x60
>>>> [ 92.277054] migrate_vma_collect+0xf6/0x100
>>>> [ 92.277055] migrate_vma_setup+0xcf/0x120
>>>> [ 92.277109] svm_migrate_ram_to_vram+0x256/0x6b0 [amdgpu]
>>>>
>>>> 2.Call svm_range_map_to_gpu->amdgpu_vm_update_range to update the
>>>> page table, at this time it will use the same entry bo which is the
>>>> want free bo in step1.
>>>>
>>>> 3.Then it executes the pt_free_work to free the bo. At this time,
>>>> the GPU access memory will cause page fault as pt bo has been freed.
>>>> And then it will call svm_range_restore_pages again.
>>>>
>>>> How to fix?
>>>> Add a workqueue, and flush the workqueue each time before updating page
>table.
>>>
>>>I think this is kind of a known issue in the GPUVM code. Philip was
>>>looking at it before.
>>>
>>>Just flushing a workqueue may seem like a simple and elegant solution,
>>>but I'm afraid it introduces lock dependency issues. By flushing the
>>>workqueue, you're effectively creating a lock dependency of the MMU
>>>notifier on any locks held inside the worker function. You now get a
>>>circular lock dependency with any of those locks and memory reclaim. I
>>>think LOCKDEP would be able to catch that if you compile your kernel
>>>with that
>>feature enabled.
>>>
>>>The proper solution is to prevent delayed freeing of page tables if
>>>they happened to get reused, or prevent reuse of page tables if they
>>>are flagged for
>>delayed freeing.
>>>
>>>Regards,
>>> Felix
>>>
>>Thanks, already enabled LOCKDEP while compiling the kernel. The delay
>>work seems for other reasons, I am not sure whether it could be deleted completely.
>>
>>Emily Deng
>>Best Wishes
>>>
>>>>
>>>> Signed-off-by: Emily Deng <Emily.Deng@xxxxxxx>
>>>> ---
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 1 +
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 1 +
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 7 +++++--
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 6 +++++-
>>>> drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 +++
>>>> 5 files changed, 15 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> index 93c352b08969..cbf68ad1c8d0 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> @@ -1188,6 +1188,7 @@ struct amdgpu_device {
>>>> struct mutex enforce_isolation_mutex;
>>>>
>>>> struct amdgpu_init_level *init_lvl;
>>>> + struct workqueue_struct *wq;
>>>> };
>>>>
>>>> static inline uint32_t amdgpu_ip_version(const struct
>>>> amdgpu_device *adev, diff --git
>>>> a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> index f30548f4c3b3..5b4835bc81b3 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> @@ -2069,6 +2069,7 @@ int amdgpu_amdkfd_gpuvm_map_memory_to_gpu(
>>>> if (ret)
>>>> goto out;
>>>> }
>>>> + flush_workqueue(adev->wq);
>>>>
>>>> ret = reserve_bo_and_vm(mem, avm, &ctx);
>>>> if (unlikely(ret))
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>> index 9d6ffe38b48a..500d97cd9114 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>> @@ -2607,7 +2607,7 @@ void amdgpu_vm_fini(struct amdgpu_device
>>>> *adev,
>>>struct amdgpu_vm *vm)
>>>> amdgpu_amdkfd_gpuvm_destroy_cb(adev, vm);
>>>>
>>>> flush_work(&vm->pt_free_work);
>>>> -
>>>> + cancel_work_sync(&vm->pt_free_work);
>>>> root = amdgpu_bo_ref(vm->root.bo);
>>>> amdgpu_bo_reserve(root, true);
>>>> amdgpu_vm_put_task_info(vm->task_info);
>>>> @@ -2708,6 +2708,8 @@ void amdgpu_vm_manager_init(struct
>>>> amdgpu_device
>>>*adev)
>>>> #endif
>>>>
>>>> xa_init_flags(&adev->vm_manager.pasids, XA_FLAGS_LOCK_IRQ);
>>>> + adev->wq = alloc_workqueue("amdgpu_recycle",
>>>> + WQ_MEM_RECLAIM | WQ_HIGHPRI |
>>>WQ_UNBOUND, 16);
>>>> }
>>>>
>>>> /**
>>>> @@ -2721,7 +2723,8 @@ void amdgpu_vm_manager_fini(struct
>>>> amdgpu_device
>>>*adev)
>>>> {
>>>> WARN_ON(!xa_empty(&adev->vm_manager.pasids));
>>>> xa_destroy(&adev->vm_manager.pasids);
>>>> -
>>>> + flush_workqueue(adev->wq);
>>>> + destroy_workqueue(adev->wq);
>>>> amdgpu_vmid_mgr_fini(adev);
>>>> }
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
>>>> index f78a0434a48f..1204406215ee 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
>>>> @@ -554,15 +554,19 @@ void amdgpu_vm_pt_free_work(struct work_struct
>>>> *work)
>>>>
>>>> vm = container_of(work, struct amdgpu_vm, pt_free_work);
>>>>
>>>> + printk("Emily:%s\n", __func__);
>>>> spin_lock(&vm->status_lock);
>>>> list_splice_init(&vm->pt_freed, &pt_freed);
>>>> spin_unlock(&vm->status_lock);
>>>> + printk("Emily:%s 1\n", __func__);
>>>>
>>>> /* flush_work in amdgpu_vm_fini ensure vm->root.bo is valid. */
>>>> amdgpu_bo_reserve(vm->root.bo, true);
>>>> + printk("Emily:%s 2\n", __func__);
>>>>
>>>> list_for_each_entry_safe(entry, next, &pt_freed, vm_status)
>>>> amdgpu_vm_pt_free(entry);
>>>> + printk("Emily:%s 3\n", __func__);
>>>>
>>>> amdgpu_bo_unreserve(vm->root.bo);
>>>> }
>>>> @@ -589,7 +593,7 @@ void amdgpu_vm_pt_free_list(struct amdgpu_device
>>>*adev,
>>>> spin_lock(&vm->status_lock);
>>>> list_splice_init(¶ms->tlb_flush_waitlist, &vm->pt_freed);
>>>> spin_unlock(&vm->status_lock);
>>>> - schedule_work(&vm->pt_free_work);
>>>> + queue_work(adev->wq, &vm->pt_free_work);
>>>> return;
>>>> }
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>> index 3e2911895c74..55edf96d5a95 100644
>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>>> @@ -1314,6 +1314,7 @@ svm_range_unmap_from_gpu(struct amdgpu_device
>>>*adev, struct amdgpu_vm *vm,
>>>> uint64_t init_pte_value = 0;
>>>>
>>>> pr_debug("[0x%llx 0x%llx]\n", start, last);
>>>> + flush_workqueue(adev->wq);
>>>>
>>>> return amdgpu_vm_update_range(adev, vm, false, true, true,
>>>> false, NULL,
>>>start,
>>>> last, init_pte_value, 0, 0, NULL,
>>>> NULL, @@ -1422,6
>>>+1423,8
>>>> @@ svm_range_map_to_gpu(struct kfd_process_device *pdd, struct
>>>> svm_range
>>>*prange,
>>>> * different memory partition based on fpfn/lpfn, we should use
>>>> * same vm_manager.vram_base_offset regardless memory partition.
>>>> */
>>>> + flush_workqueue(adev->wq);
>>>> +
>>>> r = amdgpu_vm_update_range(adev, vm, false, false, flush_tlb, true,
>>>> NULL, last_start, prange->start + i,
>>>> pte_flags,
