Re: [Intel-gfx] [PATCH 2/2] drm/ttm, drm/i915: Update ttm_move_memcpy for async use

["Christian König" <christian.koenig@amd.com>]

Am 28.06.21 um 13:21 schrieb Thomas Hellström:
>
> On 6/24/21 9:30 PM, Thomas Hellström wrote:
>> The buffer object argument to ttm_move_memcpy was only used to
>> determine whether the destination memory should be cleared only
>> or whether we should copy data. Replace it with a "clear" bool, and
>> update the callers.
>>
>> The intention here is to be able to use ttm_move_memcpy() async under
>> a dma-fence as a fallback if an accelerated blit fails in a security-
>> critical path where data might leak if the blit is not properly
>> performed. For that purpose the bo is an unsuitable argument since
>> its relevant members might already have changed at call time.
>>
>> Finally, update the ttm_move_memcpy kerneldoc that seems to have
>> ended up with a stale version.
>
> Hmm,
>
> Not sure where the Cc: Christian König ended up, but in any case 
> Christian if you find this patch ok, Ack to merge through 
> drm_intel_gt_next?

Please send out the patch once more.

Only nit picks, but I would re-order the parameters for example.

Regards,
Christian.

>
> /Thomas
>
>
>
>
>>
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c |  2 +-
>>   drivers/gpu/drm/ttm/ttm_bo_util.c       | 20 ++++++++++----------
>>   include/drm/ttm/ttm_bo_driver.h         |  2 +-
>>   3 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c 
>> b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> index 4e529adcdfc7..f19847abe856 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>> @@ -517,7 +517,7 @@ static void __i915_ttm_move(struct 
>> ttm_buffer_object *bo, bool clear,
>>                            obj->ttm.cached_io_st,
>>                            src_reg->region.start);
>>   -        ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
>> +        ttm_move_memcpy(clear, dst_mem->num_pages, dst_iter, src_iter);
>>       }
>>   }
>>   diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c 
>> b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> index 2f57f824e6db..e3747f069674 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
>> @@ -75,22 +75,21 @@ void ttm_mem_io_free(struct ttm_device *bdev,
>>     /**
>>    * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
>> - * @bo: The struct ttm_buffer_object.
>> - * @new_mem: The struct ttm_resource we're moving to (copy 
>> destination).
>> - * @new_iter: A struct ttm_kmap_iter representing the destination 
>> resource.
>> + * @clear: Whether to clear rather than copy.
>> + * @num_pages: Number of pages of the operation.
>> + * @dst_iter: A struct ttm_kmap_iter representing the destination 
>> resource.
>>    * @src_iter: A struct ttm_kmap_iter representing the source resource.
>>    *
>>    * This function is intended to be able to move out async under a
>>    * dma-fence if desired.
>>    */
>> -void ttm_move_memcpy(struct ttm_buffer_object *bo,
>> +void ttm_move_memcpy(bool clear,
>>                u32 num_pages,
>>                struct ttm_kmap_iter *dst_iter,
>>                struct ttm_kmap_iter *src_iter)
>>   {
>>       const struct ttm_kmap_iter_ops *dst_ops = dst_iter->ops;
>>       const struct ttm_kmap_iter_ops *src_ops = src_iter->ops;
>> -    struct ttm_tt *ttm = bo->ttm;
>>       struct dma_buf_map src_map, dst_map;
>>       pgoff_t i;
>>   @@ -99,10 +98,7 @@ void ttm_move_memcpy(struct ttm_buffer_object *bo,
>>           return;
>>         /* Don't move nonexistent data. Clear destination instead. */
>> -    if (src_ops->maps_tt && (!ttm || !ttm_tt_is_populated(ttm))) {
>> -        if (ttm && !(ttm->page_flags & TTM_PAGE_FLAG_ZERO_ALLOC))
>> -            return;
>> -
>> +    if (clear) {
>>           for (i = 0; i < num_pages; ++i) {
>>               dst_ops->map_local(dst_iter, &dst_map, i);
>>               if (dst_map.is_iomem)
>> @@ -146,6 +142,7 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
>>           struct ttm_kmap_iter_linear_io io;
>>       } _dst_iter, _src_iter;
>>       struct ttm_kmap_iter *dst_iter, *src_iter;
>> +    bool clear;
>>       int ret = 0;
>>         if (ttm && ((ttm->page_flags & TTM_PAGE_FLAG_SWAPPED) ||
>> @@ -169,7 +166,10 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object 
>> *bo,
>>           goto out_src_iter;
>>       }
>>   -    ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
>> +    clear = src_iter->ops->maps_tt && (!ttm || 
>> !ttm_tt_is_populated(ttm));
>> +    if (!(clear && ttm && !(ttm->page_flags & 
>> TTM_PAGE_FLAG_ZERO_ALLOC)))
>> +        ttm_move_memcpy(clear, dst_mem->num_pages, dst_iter, src_iter);
>> +
>>       src_copy = *src_mem;
>>       ttm_bo_move_sync_cleanup(bo, dst_mem);
>>   diff --git a/include/drm/ttm/ttm_bo_driver.h 
>> b/include/drm/ttm/ttm_bo_driver.h
>> index 68d6069572aa..5f087575194b 100644
>> --- a/include/drm/ttm/ttm_bo_driver.h
>> +++ b/include/drm/ttm/ttm_bo_driver.h
>> @@ -322,7 +322,7 @@ int ttm_bo_tt_bind(struct ttm_buffer_object *bo, 
>> struct ttm_resource *mem);
>>    */
>>   void ttm_bo_tt_destroy(struct ttm_buffer_object *bo);
>>   -void ttm_move_memcpy(struct ttm_buffer_object *bo,
>> +void ttm_move_memcpy(bool clear,
>>                u32 num_pages,
>>                struct ttm_kmap_iter *dst_iter,
>>                struct ttm_kmap_iter *src_iter);

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