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

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

Am 01.11.24 um 00:43 schrieb Matthew Brost:
> 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?

I don't see the original patch anywhere in my inbox, please make sure to 
CC me while sending things out.

Apart from that I absolutely don't see any justification for this patch. 
You move stuff into ttm_bo_util.c which not even remotely belongs in there.

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
>>