[AMD Official Use Only - General]
>-----Original Message-----
>From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
>Sent: Saturday, January 27, 2024 3:22 AM
>To: Yu, Lang <Lang.Yu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
>Cc: Francis, David <David.Francis@xxxxxxx>
>Subject: Re: [PATCH v2] drm/amdkfd: reserve the BO before validating it
>
>
>On 2024-01-25 20:59, Yu, Lang wrote:
>> [AMD Official Use Only - General]
>>
>>> -----Original Message-----
>>> From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
>>> Sent: Thursday, January 25, 2024 5:41 AM
>>> To: Yu, Lang <Lang.Yu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
>>> Cc: Francis, David <David.Francis@xxxxxxx>
>>> Subject: Re: [PATCH v2] drm/amdkfd: reserve the BO before validating
>>> it
>>>
>>> On 2024-01-22 4:08, Lang Yu wrote:
>>>> Fixes: 410f08516e0f ("drm/amdkfd: Move dma unmapping after TLB
>>>> flush")
>>>>
>>>> v2:
>>>> Avoid unmapping attachment twice when ERESTARTSYS.
>>>>
>>>> [ 41.708711] WARNING: CPU: 0 PID: 1463 at
>>> drivers/gpu/drm/ttm/ttm_bo.c:846 ttm_bo_validate+0x146/0x1b0 [ttm]
>>>> [ 41.708989] Call Trace:
>>>> [ 41.708992] <TASK>
>>>> [ 41.708996] ? show_regs+0x6c/0x80
>>>> [ 41.709000] ? ttm_bo_validate+0x146/0x1b0 [ttm]
>>>> [ 41.709008] ? __warn+0x93/0x190
>>>> [ 41.709014] ? ttm_bo_validate+0x146/0x1b0 [ttm]
>>>> [ 41.709024] ? report_bug+0x1f9/0x210
>>>> [ 41.709035] ? handle_bug+0x46/0x80
>>>> [ 41.709041] ? exc_invalid_op+0x1d/0x80
>>>> [ 41.709048] ? asm_exc_invalid_op+0x1f/0x30
>>>> [ 41.709057] ? amdgpu_amdkfd_gpuvm_dmaunmap_mem+0x2c/0x80
>>> [amdgpu]
>>>> [ 41.709185] ? ttm_bo_validate+0x146/0x1b0 [ttm]
>>>> [ 41.709197] ? amdgpu_amdkfd_gpuvm_dmaunmap_mem+0x2c/0x80
>>> [amdgpu]
>>>> [ 41.709337] ? srso_alias_return_thunk+0x5/0x7f
>>>> [ 41.709346] kfd_mem_dmaunmap_attachment+0x9e/0x1e0 [amdgpu]
>>>> [ 41.709467] amdgpu_amdkfd_gpuvm_dmaunmap_mem+0x56/0x80
>>> [amdgpu]
>>>> [ 41.709586] kfd_ioctl_unmap_memory_from_gpu+0x1b7/0x300 [amdgpu]
>>>> [ 41.709710] kfd_ioctl+0x1ec/0x650 [amdgpu]
>>>> [ 41.709822] ? __pfx_kfd_ioctl_unmap_memory_from_gpu+0x10/0x10
>>> [amdgpu]
>>>> [ 41.709945] ? srso_alias_return_thunk+0x5/0x7f
>>>> [ 41.709949] ? tomoyo_file_ioctl+0x20/0x30
>>>> [ 41.709959] __x64_sys_ioctl+0x9c/0xd0
>>>> [ 41.709967] do_syscall_64+0x3f/0x90
>>>> [ 41.709973] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>>>>
>>>> Signed-off-by: Lang Yu <Lang.Yu@xxxxxxx>
>>>> ---
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h | 2 +-
>>>> .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 28
>>> +++++++++++++++++--
>>>> drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 4 ++-
>>>> 3 files changed, 29 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
>>>> index 584a0cea5572..41854417e487 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
>>>> @@ -311,7 +311,7 @@ int
>>> amdgpu_amdkfd_gpuvm_map_memory_to_gpu(struct amdgpu_device *adev,
>>>> struct kgd_mem *mem, void
>>> *drm_priv);
>>>> int amdgpu_amdkfd_gpuvm_unmap_memory_from_gpu(
>>>> struct amdgpu_device *adev, struct kgd_mem *mem, void
>>> *drm_priv);
>>>> -void amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct kgd_mem *mem, void
>>>> *drm_priv);
>>>> +int amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct kgd_mem *mem, void
>>>> +*drm_priv);
>>>> int amdgpu_amdkfd_gpuvm_sync_memory(
>>>> struct amdgpu_device *adev, struct kgd_mem *mem, bool intr);
>>>> int amdgpu_amdkfd_gpuvm_map_gtt_bo_to_kernel(struct kgd_mem *mem,
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> index 6f3a4cb2a9ef..7a050d46fa4d 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>> @@ -2088,21 +2088,43 @@ int
>>> amdgpu_amdkfd_gpuvm_map_memory_to_gpu(
>>>> return ret;
>>>> }
>>>>
>>>> -void amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct kgd_mem *mem, void
>>>> *drm_priv)
>>>> +int amdgpu_amdkfd_gpuvm_dmaunmap_mem(struct kgd_mem *mem, void
>>>> +*drm_priv)
>>>> {
>>>> struct kfd_mem_attachment *entry;
>>>> struct amdgpu_vm *vm;
>>>> + bool reserved = false;
>>>> + int ret = 0;
>>>>
>>>> vm = drm_priv_to_vm(drm_priv);
>>>>
>>>> mutex_lock(&mem->lock);
>>>>
>>>> list_for_each_entry(entry, &mem->attachments, list) {
>>>> - if (entry->bo_va->base.vm == vm)
>>>> - kfd_mem_dmaunmap_attachment(mem, entry);
>>>> + if (entry->bo_va->base.vm != vm)
>>>> + continue;
>>>> + if (entry->type == KFD_MEM_ATT_SHARED ||
>>>> + entry->type == KFD_MEM_ATT_DMABUF)
>>>> + continue;
>>>> + if (!entry->bo_va->base.bo->tbo.ttm->sg)
>>>> + continue;
>>> You're going to great lengths to avoid the reservation when it's not
>>> needed by kfd_mem_dmaunmap_attachment. However, this feels a bit
>>> fragile. Any changes in the kfd_mem_dmaunmap_* functions could break this.
>>>
>>>> +
>>>> + if (!reserved) {
>>>> + ret = amdgpu_bo_reserve(mem->bo, true);
>>>> + if (ret)
>>>> + goto out;
>>>> + reserved = true;
>>>> + }
>>>> +
>>>> + kfd_mem_dmaunmap_attachment(mem, entry);
>>>> }
>>>>
>>>> + if (reserved)
>>>> + amdgpu_bo_unreserve(mem->bo);
>>>> +
>>>> +out:
>>>> mutex_unlock(&mem->lock);
>>>> +
>>>> + return ret;
>>>> }
>>>>
>>>> int amdgpu_amdkfd_gpuvm_unmap_memory_from_gpu(
>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>> index ce4c52ec34d8..80e90fdef291 100644
>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>> @@ -1442,7 +1442,9 @@ static int
>>>> kfd_ioctl_unmap_memory_from_gpu(struct
>>> file *filep,
>>>> kfd_flush_tlb(peer_pdd,
>>>> TLB_FLUSH_HEAVYWEIGHT);
>>>>
>>>> /* Remove dma mapping after tlb flush to avoid
>>>> IO_PAGE_FAULT
>>> */
>>>> - amdgpu_amdkfd_gpuvm_dmaunmap_mem(mem, peer_pdd-
>>>> drm_priv);
>>>> + err = amdgpu_amdkfd_gpuvm_dmaunmap_mem(mem,
>>> peer_pdd->drm_priv);
>>>> + if (err)
>>>> + goto sync_memory_failed;
>>> This handles the case that the system call got interrupted. But
>>> you're not handling the restart correctly. When the ioctl is
>>> restarted, you don't know how many dmaunmaps are already done. So
>>> you'd need to make sure that repeating the dmaunmap is safe in all
>>> cases. Or what David tried earlier, find a way to track the unmapping so you
>only try to dmaunmap on GPUs where it's actually dmamapped.
>> From previous discussion, no one likes add another variable to track the
>unmappings. So I'm avoiding adding another variable.
>>
>> Actually, all memory attachments use sg_table, ttm->sg is NULL? can be used as
>an indicator to see whether an attachment is already unmapped.
>> That already unmapped will not be repeated.
>
>I think that should work. I'd add the checks in kfd_mem_dmaunmap_userptr and
>kfd_mem_dmaunmap_sg_bo, where we also set ttm->sg to NULL. In fact, both
>those functions already have that check. So looks like it should handle the the
>restart correctly with your patch.
Yes, both kfd_mem_dmaunmap_userptr() and kfd_mem_dmaunmap_sg_bo() have NULL check for ttm->sg.
And dmabuf also have this check in amdgpu_ttm_backend_unbind(). So dmaunmap won't be repeated actually.
Then the benefits of handling ERESTARTSYS is avoiding amdgpu_bo_reserve().
What do you think? It's worth avoiding reservation in this case?
Regards,
Lang
>Regards,
> Felix
>
>
>>
>> Regards,
>> Lang
>>
>>> Regards,
>>> Felix
>>>
>>>
>>>> }
>>>>
>>>> mutex_unlock(&p->mutex);
