[PATCH v2] drm/amdkfd: reserve the BO before validating it
Yu, Lang
Lang.Yu at amd.com
Tue Jan 30 02:23:15 UTC 2024
[Public]
>-----Original Message-----
>From: Kuehling, Felix <Felix.Kuehling at amd.com>
>Sent: Monday, January 29, 2024 10:58 PM
>To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>Cc: Francis, David <David.Francis at amd.com>
>Subject: Re: [PATCH v2] drm/amdkfd: reserve the BO before validating it
>
>On 2024-01-28 21:30, Yu, Lang wrote:
>> [AMD Official Use Only - General]
>>
>>> -----Original Message-----
>>> From: Kuehling, Felix <Felix.Kuehling at amd.com>
>>> Sent: Saturday, January 27, 2024 3:22 AM
>>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>>> Cc: Francis, David <David.Francis at amd.com>
>>> 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 at amd.com>
>>>>> Sent: Thursday, January 25, 2024 5:41 AM
>>>>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>>>>> Cc: Francis, David <David.Francis at amd.com>
>>>>> 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 at amd.com>
>>>>>> ---
>>>>>> 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?
>
>I don't think it's worth the trouble. In fact, to avoid race conditions, you probably
>should take the reservation anyway before looking at ttm->sg.
Got it. Thanks.
Regards,
Lang
>Regards,
> Felix
>
>
>>
>> Regards,
>> Lang
>>
>>> Regards,
>>> Felix
>>>
>>>
>>>> Regards,
>>>> Lang
>>>>
>>>>> Regards,
>>>>> Felix
>>>>>
>>>>>
>>>>>> }
>>>>>>
>>>>>> mutex_unlock(&p->mutex);
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