[PATCH 8/9] drm/shmem-helpers: Ensure get_pages is not called on imported dma-buf

[Thomas Zimmermann]

Hi

Am 03.06.20 um 15:12 schrieb Daniel Vetter:
> On Thu, May 14, 2020 at 09:30:04AM +0200, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 11.05.20 um 11:35 schrieb Daniel Vetter:
>>> Just a bit of light paranoia. Also sprinkle this check over
>>> drm_gem_shmem_get_sg_table, which should only be called when
>>> exporting, same for the pin/unpin functions, on which it relies to
>>> work correctly.
>>>
>>> Cc: Gerd Hoffmann <kraxel at redhat.com>
>>> Cc: Rob Herring <robh at kernel.org>
>>> Cc: Noralf Trønnes <noralf at tronnes.org>
>>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>>> ---
>>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> index 117a7841e284..f7011338813e 100644
>>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> @@ -170,6 +170,8 @@ int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
>>>  {
>>>  	int ret;
>>>  
>>> +	WARN_ON(shmem->base.import_attach);
>>> +
>>>  	ret = mutex_lock_interruptible(&shmem->pages_lock);
>>>  	if (ret)
>>>  		return ret;
>>> @@ -225,6 +227,8 @@ int drm_gem_shmem_pin(struct drm_gem_object *obj)
>>>  {
>>>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
>>>  
>>> +	WARN_ON(shmem->base.import_attach);
>>> +
>>
>> I don't understand this change. If a driver pins pages it now has to
>> check that the pages are not imported?
> 
> Nope. There's two classes of functions in the helpers, and I'm trying to
> unconfuse them:
> 
> - stuff used to implement gem_funcs. These are obviously only ever used on
>   native objects, never on imported ones (on imported ones we try to
>   forward through the dma-buf layer to the exporter). drm_gem_shmem_pin is
>   only used in that role to implement gem_funcs->pin. Calling it on an
>   imported buffer is indeed a bug.
> 
> - the other set of functions are for drivers to do their stuff. The
>   interface which (implicitly) pins stuff into places is various set of
>   get_pages, which do have different paths for native and imported
>   objects.

Thanks for explaining. Patch is

Acked-by: Thomas Zimmermann <tzimmermann at suse.de>

> 
> Apologies that I missed your question here, I merged all the patches
> leading up to this one for now.
> 
> Thanks, Daniel
> 
>>
>>
>>>  	return drm_gem_shmem_get_pages(shmem);
>>>  }
>>>  EXPORT_SYMBOL(drm_gem_shmem_pin);
>>> @@ -240,6 +244,8 @@ void drm_gem_shmem_unpin(struct drm_gem_object *obj)
>>>  {
>>>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
>>>  
>>> +	WARN_ON(shmem->base.import_attach);
>>> +
>>>  	drm_gem_shmem_put_pages(shmem);
>>>  }
>>>  EXPORT_SYMBOL(drm_gem_shmem_unpin);
>>> @@ -510,6 +516,8 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>>>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
>>>  	int ret;
>>>  
>>> +	WARN_ON(shmem->base.import_attach);
>>> +
>>>  	ret = drm_gem_shmem_get_pages(shmem);
>>>  	WARN_ON_ONCE(ret != 0);
>>>  
>>> @@ -611,6 +619,8 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
>>>  {
>>>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
>>>  
>>> +	WARN_ON(shmem->base.import_attach);
>>> +
>>>  	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT);
>>>  }
>>>  EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
>>>
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Felix Imendörffer
>>
> 
> 
> 
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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