Re: [Spice-devel] [PATCH 1/2] drm/qxl: stop abusing TTM to call driver internal functions

[Frediano Ziglio <fziglio@redhat.com>]

> 
> Am 27.09.19 um 18:31 schrieb Frediano Ziglio:
> >> The ttm_mem_io_* functions are actually internal to TTM and shouldn't be
> >> used in a driver.
> >>
> > As far as I can see by your second patch QXL is just using exported
> > (that is not internal) functions.
> > Not that the idea of making them internal is bad but this comment is
> > a wrong statement.
> 
> See the history of exporting those, that was done specifically so that
> QXL can call them (commit afe6804c045fbd69a1b75c681107b5d6df9190de).
> 
> But those are the internal functions which TTM uses to call into the
> driver. That a driver uses them to call into itself doesn't seem to make
> sense.
> 

The commit was merged and release in Linux 3.10 6 years ago, since
then these functions have been exported. Not saying that the QXL change
was wrong and should not have been acked and merged but after 6 years
saying that these functions are internal it's not correct.

Something like

"The ttm_mem_io_* functions were intended to be internal to TTM and
shouldn't have been used in a driver. They were exported in commit
afe6804c045fbd69a1b75c681107b5d6df9190de just for QXL."

> >> Instead call the qxl_ttm_io_mem_reserve() function directly.
> >>
> > I would add that qxl_ttm_io_mem_free is empty so the removal of
> > ttm_mem_io_free is fine.
> 
> Good point, going to add that.
> 
> Thanks,
> Christian.
> 

Frediano

> >
> >> Signed-off-by: Christian König <christian.koenig@amd.com>
> >> ---
> >>   drivers/gpu/drm/qxl/qxl_drv.h    |  2 ++
> >>   drivers/gpu/drm/qxl/qxl_object.c | 11 +----------
> >>   drivers/gpu/drm/qxl/qxl_ttm.c    |  4 ++--
> >>   3 files changed, 5 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/qxl/qxl_drv.h b/drivers/gpu/drm/qxl/qxl_drv.h
> >> index 9e034c5fa87d..8a24f8e101da 100644
> >> --- a/drivers/gpu/drm/qxl/qxl_drv.h
> >> +++ b/drivers/gpu/drm/qxl/qxl_drv.h
> >> @@ -354,6 +354,8 @@ int qxl_mode_dumb_mmap(struct drm_file *filp,
> >>   /* qxl ttm */
> >>   int qxl_ttm_init(struct qxl_device *qdev);
> >>   void qxl_ttm_fini(struct qxl_device *qdev);
> >> +int qxl_ttm_io_mem_reserve(struct ttm_bo_device *bdev,
> >> +			   struct ttm_mem_reg *mem);
> >>   int qxl_mmap(struct file *filp, struct vm_area_struct *vma);
> >>   
> >>   /* qxl image */
> >> diff --git a/drivers/gpu/drm/qxl/qxl_object.c
> >> b/drivers/gpu/drm/qxl/qxl_object.c
> >> index 548dfe6f3b26..299e63a951c5 100644
> >> --- a/drivers/gpu/drm/qxl/qxl_object.c
> >> +++ b/drivers/gpu/drm/qxl/qxl_object.c
> >> @@ -148,7 +148,6 @@ int qxl_bo_kmap(struct qxl_bo *bo, void **ptr)
> >>   void *qxl_bo_kmap_atomic_page(struct qxl_device *qdev,
> >>   			      struct qxl_bo *bo, int page_offset)
> >>   {
> >> -	struct ttm_mem_type_manager *man =
> >> &bo->tbo.bdev->man[bo->tbo.mem.mem_type];
> >>   	void *rptr;
> >>   	int ret;
> >>   	struct io_mapping *map;
> >> @@ -160,9 +159,7 @@ void *qxl_bo_kmap_atomic_page(struct qxl_device *qdev,
> >>   	else
> >>   		goto fallback;
> >>   
> >> -	(void) ttm_mem_io_lock(man, false);
> >> -	ret = ttm_mem_io_reserve(bo->tbo.bdev, &bo->tbo.mem);
> >> -	ttm_mem_io_unlock(man);
> >> +	ret = qxl_ttm_io_mem_reserve(bo->tbo.bdev, &bo->tbo.mem);
> >>   
> >>   	return io_mapping_map_atomic_wc(map, bo->tbo.mem.bus.offset +
> >>   	page_offset);
> >>   fallback:
> >> @@ -193,17 +190,11 @@ void qxl_bo_kunmap(struct qxl_bo *bo)
> >>   void qxl_bo_kunmap_atomic_page(struct qxl_device *qdev,
> >>   			       struct qxl_bo *bo, void *pmap)
> >>   {
> >> -	struct ttm_mem_type_manager *man =
> >> &bo->tbo.bdev->man[bo->tbo.mem.mem_type];
> >> -
> >>   	if ((bo->tbo.mem.mem_type != TTM_PL_VRAM) &&
> >>   	    (bo->tbo.mem.mem_type != TTM_PL_PRIV))
> >>   		goto fallback;
> >>   
> >>   	io_mapping_unmap_atomic(pmap);
> >> -
> >> -	(void) ttm_mem_io_lock(man, false);
> >> -	ttm_mem_io_free(bo->tbo.bdev, &bo->tbo.mem);
> >> -	ttm_mem_io_unlock(man);
> >>   	return;
> >>    fallback:
> >>   	qxl_bo_kunmap(bo);
> >> diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
> >> index 9b24514c75aa..cb80e512dd46 100644
> >> --- a/drivers/gpu/drm/qxl/qxl_ttm.c
> >> +++ b/drivers/gpu/drm/qxl/qxl_ttm.c
> >> @@ -159,8 +159,8 @@ static int qxl_verify_access(struct ttm_buffer_object
> >> *bo, struct file *filp)
> >>   					  filp->private_data);
> >>   }
> >>   
> >> -static int qxl_ttm_io_mem_reserve(struct ttm_bo_device *bdev,
> >> -				  struct ttm_mem_reg *mem)
> >> +int qxl_ttm_io_mem_reserve(struct ttm_bo_device *bdev,
> >> +			   struct ttm_mem_reg *mem)
> >>   {
> >>   	struct ttm_mem_type_manager *man = &bdev->man[mem->mem_type];
> >>   	struct qxl_device *qdev = qxl_get_qdev(bdev);
> > Otherwise fine for me.
> >
> > Frediano
> 
> 
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