Re: [PATCH 3/4] drm/amdgpu: drm/amdgpu: Handle IOMMU enabled case

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 26.08.21 um 15:43 schrieb Andrey Grodzovsky:
> Ping
>
> Andrey
>
> On 2021-08-25 11:36 a.m., Andrey Grodzovsky wrote:
>>
>> On 2021-08-25 2:43 a.m., Christian König wrote:
>>>
>>>
>>> Am 24.08.21 um 23:01 schrieb Andrey Grodzovsky:
>>>> Handle all DMA IOMMU group related dependencies before the
>>>> group is removed and we try to access it after free.
>>>>
>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  2 +
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c    | 50 
>>>> ++++++++++++++++++++++
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h    |  1 +
>>>>   3 files changed, 53 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> index 0b5764aa98a4..288a465b8101 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> @@ -3860,6 +3860,8 @@ void amdgpu_device_fini_hw(struct 
>>>> amdgpu_device *adev)
>>>>         amdgpu_device_ip_fini_early(adev);
>>>>   +    amdgpu_ttm_clear_dma_mappings(adev);
>>>> +
>>>>       amdgpu_gart_dummy_page_fini(adev);
>>>>         amdgpu_device_unmap_mmio(adev);
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>>> index 446943e32e3e..f73d807db3b0 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>>> @@ -64,6 +64,7 @@
>>>>   static int amdgpu_ttm_backend_bind(struct ttm_device *bdev,
>>>>                      struct ttm_tt *ttm,
>>>>                      struct ttm_resource *bo_mem);
>>>> +
>>>>   static void amdgpu_ttm_backend_unbind(struct ttm_device *bdev,
>>>>                         struct ttm_tt *ttm);
>>>>   @@ -2293,6 +2294,55 @@ static ssize_t amdgpu_iomem_write(struct 
>>>> file *f, const char __user *buf,
>>>>       return result;
>>>>   }
>>>>   +void amdgpu_ttm_clear_dma_mappings(struct amdgpu_device *adev)
>>>
>>> I strongly think that this function should be part of TTM. Something 
>>> like ttm_device_force_unpopulate.
>>
>>
>> Yes, this something I also wanted but see bellow
>>
>>
>>>
>>>> +{
>>>> +    struct ttm_device *bdev = &adev->mman.bdev;
>>>> +    struct ttm_resource_manager *man;
>>>> +    struct ttm_buffer_object *bo;
>>>> +    unsigned int i, j;
>>>> +
>>>> +    spin_lock(&bdev->lru_lock);
>>>> +    for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {
>>>> +        man = ttm_manager_type(bdev, i);
>>>> +        if (!man || !man->use_tt)
>>>> +            continue;
>>>> +
>>>> +        while (!list_empty(&man->pinned)) {
>>>> +            bo = list_first_entry(&man->pinned, struct 
>>>> ttm_buffer_object, lru);
>>>> +            /* Take ref against racing releases once lru_lock is 
>>>> unlocked */
>>>> +            ttm_bo_get(bo);
>>>> +            list_del_init(&bo->lru);
>>>> +            spin_unlock(&bdev->lru_lock);
>>>> +
>>>> +            if (bo->ttm) {
>>>> +                amdgpu_ttm_backend_unbind(bo->bdev, bo->ttm);
>>
>>
>> amdgpu_ttm_backend_unbind is needed to be called separately from 
>> ttm_tt_unpopulate to take care of code
>> flows that do dma mapping though the gart bind and not through 
>> ttm_tt_populate, Since it's inside amdgpu
>> i had to place the entire function in amdgpu. Any suggestions ?

I think I've fixed exactly that just recently, see the patch here:

commit b7e8b086ffbc03b890ed22ae63ed5e5bd319d184
Author: Christian König <ckoenig.leichtzumerken@gmail.com>
Date:   Wed Jul 28 15:05:49 2021 +0200

     drm/amdgpu: unbind in amdgpu_ttm_tt_unpopulate

     Doing this in amdgpu_ttm_backend_destroy() is to late.

     It turned out that this is not a good idea at all because it leaves 
pointers
     to freed up system memory pages in the GART tables of the drivers.

But that probably hasn't showed up in amd-staging-drm-next yet.

Christian.

>>
>> Andrey
>>
>>
>>>> + ttm_tt_destroy_common(bo->bdev, bo->ttm);
>>>
>>> Then you can also cleanly use ttm_tt_unpopulate here, cause this 
>>> will result in incorrect statistics inside TTM atm.
>>>
>>> Regards,
>>> Christian.
>>>
>>>> +            }
>>>> +
>>>> +            ttm_bo_put(bo);
>>>> +            spin_lock(&bdev->lru_lock);
>>>> +        }
>>>> +
>>>> +        for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
>>>> +            while (!list_empty(&man->lru[j])) {
>>>> +                bo = list_first_entry(&man->lru[j], struct 
>>>> ttm_buffer_object, lru);
>>>> +                ttm_bo_get(bo);
>>>> +                list_del_init(&bo->lru);
>>>> +                spin_unlock(&bdev->lru_lock);
>>>> +
>>>> +                if (bo->ttm) {
>>>> +                    amdgpu_ttm_backend_unbind(bo->bdev, bo->ttm);
>>>> +                    ttm_tt_destroy_common(bo->bdev, bo->ttm);
>>>> +                }
>>>> +                ttm_bo_put(bo);
>>>> +                spin_lock(&bdev->lru_lock);
>>>> +            }
>>>> +        }
>>>> +    }
>>>> +    spin_unlock(&bdev->lru_lock);
>>>> +
>>>> +}
>>>> +
>>>>   static const struct file_operations amdgpu_ttm_iomem_fops = {
>>>>       .owner = THIS_MODULE,
>>>>       .read = amdgpu_iomem_read,
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>> index e69f3e8e06e5..02c8eac48a64 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>> @@ -190,6 +190,7 @@ bool amdgpu_ttm_tt_is_readonly(struct ttm_tt 
>>>> *ttm);
>>>>   uint64_t amdgpu_ttm_tt_pde_flags(struct ttm_tt *ttm, struct 
>>>> ttm_resource *mem);
>>>>   uint64_t amdgpu_ttm_tt_pte_flags(struct amdgpu_device *adev, 
>>>> struct ttm_tt *ttm,
>>>>                    struct ttm_resource *mem);
>>>> +void amdgpu_ttm_clear_dma_mappings(struct amdgpu_device *adev);
>>>>     void amdgpu_ttm_debugfs_init(struct amdgpu_device *adev);
>>>