Re: [PATCH v2 07/10] drm/msm/gem: Rework vma lookup and pin

On 3/31/22 21:27, Dmitry Osipenko wrote:

On 3/30/22 23:47, Rob Clark wrote:

...

From: Rob Clark robdclark@chromium.org

Combines duplicate vma lookup in the get_and_pin path.

Signed-off-by: Rob Clark robdclark@chromium.org

drivers/gpu/drm/msm/msm_gem.c | 50 ++++++++++++++++++----------------- 1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c index deafae6feaa8..218744a490a4 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -376,39 +376,40 @@ put_iova_vmas(struct drm_gem_object *obj) } }

-static int get_iova_locked(struct drm_gem_object *obj,

• struct msm_gem_address_space *aspace, uint64_t *iova,
  

+static struct msm_gem_vma *get_vma_locked(struct drm_gem_object *obj,

• struct msm_gem_address_space *aspace,
  

  u64 range_start, u64 range_end)

{ struct msm_gem_vma *vma;

• int ret = 0;

  GEM_WARN_ON(!msm_gem_is_locked(obj));

  vma = lookup_vma(obj, aspace);

  if (!vma) {

• int ret;
  

• vma = add_vma(obj, aspace); if (IS_ERR(vma))

• 	return PTR_ERR(vma);
  

• 	return vma;
  
  

  ret = msm_gem_init_vma(aspace, vma, obj->size, range_start, range_end); if (ret) {

You're allocation range_start -> range_end

*allocating

...

	del_vma(vma);

• 	return ret;
  

• 	return ERR_PTR(ret);
  

  }
• } else {

• GEM_WARN_ON(vma->iova < range_start);
  

• GEM_WARN_ON((vma->iova + obj->size) > range_end);
  

and then comparing range_start -> range_start + obj->size, hence you're assuming that range_end always equals to obj->size during the allocation.

I'm not sure what is the idea here.. this looks inconsistent. I think you wanted to write:

GEM_WARN_ON(vma->iova < range_start);
GEM_WARN_ON(vma->iova + (vma->node.size << PAGE_SHIFT) > range_end);

But is it really useful to check whether the new range is inside of the old range? Shouldn't it be always a error to change the IOVA range without reallocating vma?

I'd expect to see:

GEM_WARN_ON(vma->iova != range_start);
GEM_WARN_ON(vma->iova + (vma->node.size << PAGE_SHIFT) != range_end);

and then error out if range mismatches.