Re: [PATCH v6 2/8] drm/ttm: Add ttm_bo_access

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

Am 04.11.24 um 18:34 schrieb Rodrigo Vivi:
> On Thu, Oct 31, 2024 at 04:43:19PM -0700, Matthew Brost wrote:
>> On Thu, Oct 31, 2024 at 11:10:42AM -0700, Matthew Brost wrote:
>>> Non-contiguous VRAM cannot easily be mapped in TTM nor can non-visible
>>> VRAM easily be accessed. Add ttm_bo_access, which is similar to
>>> ttm_bo_vm_access, to access such memory.
>>>
>>> v4:
>>>   - Fix checkpatch warnings (CI)
>>> v5:
>>>   - Fix checkpatch warnings (CI)
>>> v6:
>>>   - Fix kernel doc (Auld)
>>>
>> Christian - Do you mind if I merge patch along with the rest of the
>> series to drm-xe-next?
> Ray, Christian,
>
> ack on getting this patch to drm-xe-next?

No, we actually spend quite some time removing the single page mapping 
functionality for BOs.

You need a really good justification to bring that back.

Regards,
Christian.

>
>> Matt
>>
>>> Reported-by: Christoph Manszewski <christoph.manszewski@intel.com>
>>> Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>>> Tested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>>> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
>>> ---
>>>   drivers/gpu/drm/ttm/ttm_bo_util.c | 86 +++++++++++++++++++++++++++++++
>>>   drivers/gpu/drm/ttm/ttm_bo_vm.c   | 65 +----------------------
>>>   include/drm/ttm/ttm_bo.h          |  2 +
>>>   3 files changed, 89 insertions(+), 64 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> index d939925efa81..77e760ea7193 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>>> @@ -919,3 +919,89 @@ s64 ttm_lru_walk_for_evict(struct ttm_lru_walk *walk, struct ttm_device *bdev,
>>>   
>>>   	return progress;
>>>   }
>>> +
>>> +static int ttm_bo_access_kmap(struct ttm_buffer_object *bo,
>>> +			      unsigned long offset,
>>> +			      void *buf, int len, int write)
>>> +{
>>> +	unsigned long page = offset >> PAGE_SHIFT;
>>> +	unsigned long bytes_left = len;
>>> +	int ret;
>>> +
>>> +	/* Copy a page at a time, that way no extra virtual address
>>> +	 * mapping is needed
>>> +	 */
>>> +	offset -= page << PAGE_SHIFT;
>>> +	do {
>>> +		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
>>> +		struct ttm_bo_kmap_obj map;
>>> +		void *ptr;
>>> +		bool is_iomem;
>>> +
>>> +		ret = ttm_bo_kmap(bo, page, 1, &map);
>>> +		if (ret)
>>> +			return ret;
>>> +
>>> +		ptr = (void *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
>>> +		WARN_ON_ONCE(is_iomem);
>>> +		if (write)
>>> +			memcpy(ptr, buf, bytes);
>>> +		else
>>> +			memcpy(buf, ptr, bytes);
>>> +		ttm_bo_kunmap(&map);
>>> +
>>> +		page++;
>>> +		buf += bytes;
>>> +		bytes_left -= bytes;
>>> +		offset = 0;
>>> +	} while (bytes_left);
>>> +
>>> +	return len;
>>> +}
>>> +
>>> +/**
>>> + * ttm_bo_access - Helper to access a buffer object
>>> + *
>>> + * @bo: ttm buffer object
>>> + * @offset: access offset into buffer object
>>> + * @buf: pointer to caller memory to read into or write from
>>> + * @len: length of access
>>> + * @write: write access
>>> + *
>>> + * Utility function to access a buffer object. Useful when buffer object cannot
>>> + * be easily mapped (non-contiguous, non-visible, etc...).
>>> + *
>>> + * Returns:
>>> + * @len if successful, negative error code on failure.
>>> + */
>>> +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
>>> +		  void *buf, int len, int write)
>>> +{
>>> +	int ret;
>>> +
>>> +	if (len < 1 || (offset + len) > bo->base.size)
>>> +		return -EIO;
>>> +
>>> +	ret = ttm_bo_reserve(bo, true, false, NULL);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	switch (bo->resource->mem_type) {
>>> +	case TTM_PL_SYSTEM:
>>> +		fallthrough;
>>> +	case TTM_PL_TT:
>>> +		ret = ttm_bo_access_kmap(bo, offset, buf, len, write);
>>> +		break;
>>> +	default:
>>> +		if (bo->bdev->funcs->access_memory)
>>> +			ret = bo->bdev->funcs->access_memory
>>> +				(bo, offset, buf, len, write);
>>> +		else
>>> +			ret = -EIO;
>>> +	}
>>> +
>>> +	ttm_bo_unreserve(bo);
>>> +
>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL(ttm_bo_access);
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> index 2c699ed1963a..20b1e5f78684 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>> @@ -366,45 +366,6 @@ void ttm_bo_vm_close(struct vm_area_struct *vma)
>>>   }
>>>   EXPORT_SYMBOL(ttm_bo_vm_close);
>>>   
>>> -static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
>>> -				 unsigned long offset,
>>> -				 uint8_t *buf, int len, int write)
>>> -{
>>> -	unsigned long page = offset >> PAGE_SHIFT;
>>> -	unsigned long bytes_left = len;
>>> -	int ret;
>>> -
>>> -	/* Copy a page at a time, that way no extra virtual address
>>> -	 * mapping is needed
>>> -	 */
>>> -	offset -= page << PAGE_SHIFT;
>>> -	do {
>>> -		unsigned long bytes = min(bytes_left, PAGE_SIZE - offset);
>>> -		struct ttm_bo_kmap_obj map;
>>> -		void *ptr;
>>> -		bool is_iomem;
>>> -
>>> -		ret = ttm_bo_kmap(bo, page, 1, &map);
>>> -		if (ret)
>>> -			return ret;
>>> -
>>> -		ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
>>> -		WARN_ON_ONCE(is_iomem);
>>> -		if (write)
>>> -			memcpy(ptr, buf, bytes);
>>> -		else
>>> -			memcpy(buf, ptr, bytes);
>>> -		ttm_bo_kunmap(&map);
>>> -
>>> -		page++;
>>> -		buf += bytes;
>>> -		bytes_left -= bytes;
>>> -		offset = 0;
>>> -	} while (bytes_left);
>>> -
>>> -	return len;
>>> -}
>>> -
>>>   int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>>>   		     void *buf, int len, int write)
>>>   {
>>> @@ -412,32 +373,8 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
>>>   	unsigned long offset = (addr) - vma->vm_start +
>>>   		((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
>>>   		 << PAGE_SHIFT);
>>> -	int ret;
>>> -
>>> -	if (len < 1 || (offset + len) > bo->base.size)
>>> -		return -EIO;
>>>   
>>> -	ret = ttm_bo_reserve(bo, true, false, NULL);
>>> -	if (ret)
>>> -		return ret;
>>> -
>>> -	switch (bo->resource->mem_type) {
>>> -	case TTM_PL_SYSTEM:
>>> -		fallthrough;
>>> -	case TTM_PL_TT:
>>> -		ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);
>>> -		break;
>>> -	default:
>>> -		if (bo->bdev->funcs->access_memory)
>>> -			ret = bo->bdev->funcs->access_memory(
>>> -				bo, offset, buf, len, write);
>>> -		else
>>> -			ret = -EIO;
>>> -	}
>>> -
>>> -	ttm_bo_unreserve(bo);
>>> -
>>> -	return ret;
>>> +	return ttm_bo_access(bo, offset, buf, len, write);
>>>   }
>>>   EXPORT_SYMBOL(ttm_bo_vm_access);
>>>   
>>> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
>>> index 5804408815be..8ea11cd8df39 100644
>>> --- a/include/drm/ttm/ttm_bo.h
>>> +++ b/include/drm/ttm/ttm_bo.h
>>> @@ -421,6 +421,8 @@ void ttm_bo_unpin(struct ttm_buffer_object *bo);
>>>   int ttm_bo_evict_first(struct ttm_device *bdev,
>>>   		       struct ttm_resource_manager *man,
>>>   		       struct ttm_operation_ctx *ctx);
>>> +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
>>> +		  void *buf, int len, int write);
>>>   vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
>>>   			     struct vm_fault *vmf);
>>>   vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
>>> -- 
>>> 2.34.1
>>>