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

[Christian König <christian.koenig@xxxxxxx>]

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@xxxxxxxxxxxxxxx>
> > ---
> >   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);