Re: [Intel-gfx] [RFC v4 03/14] drm/i915/vm_bind: Expose i915_gem_object_max_page_size()

[Matthew Auld <matthew.auld@intel.com>]

On 22/09/2022 09:09, Tvrtko Ursulin wrote:
> 
> On 21/09/2022 19:00, Niranjana Vishwanathapura wrote:
>> On Wed, Sep 21, 2022 at 10:13:12AM +0100, Tvrtko Ursulin wrote:
>>>
>>> On 21/09/2022 08:09, Niranjana Vishwanathapura wrote:
>>>> Expose i915_gem_object_max_page_size() function non-static
>>>> which will be used by the vm_bind feature.
>>>>
>>>> Signed-off-by: Niranjana Vishwanathapura 
>>>> <niranjana.vishwanathapura@intel.com>
>>>> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
>>>> ---
>>>>  drivers/gpu/drm/i915/gem/i915_gem_create.c | 20 +++++++++++++++-----
>>>>  drivers/gpu/drm/i915/gem/i915_gem_object.h |  2 ++
>>>>  2 files changed, 17 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c 
>>>> b/drivers/gpu/drm/i915/gem/i915_gem_create.c
>>>> index 33673fe7ee0a..3b3ab4abb0a3 100644
>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
>>>> @@ -11,14 +11,24 @@
>>>>  #include "pxp/intel_pxp.h"
>>>>  #include "i915_drv.h"
>>>> +#include "i915_gem_context.h"
>>>
>>> I can't spot that you are adding any code which would need this? 
>>> I915_GTT_PAGE_SIZE_4K? It is in intel_gtt.h.
>>
>> This include should have been added in a later patch for calling
>> i915_gem_vm_lookup(). But got added here while patch refactoring.
>> Will fix.
>>
>>>
>>>>  #include "i915_gem_create.h"
>>>>  #include "i915_trace.h"
>>>>  #include "i915_user_extensions.h"
>>>> -static u32 object_max_page_size(struct intel_memory_region 
>>>> **placements,
>>>> -                unsigned int n_placements)
>>>> +/**
>>>> + * i915_gem_object_max_page_size() - max of min_page_size of the 
>>>> regions
>>>> + * @placements:  list of regions
>>>> + * @n_placements: number of the placements
>>>> + *
>>>> + * Calculates the max of the min_page_size of a list of placements 
>>>> passed in.
>>>> + *
>>>> + * Return: max of the min_page_size
>>>> + */
>>>> +u32 i915_gem_object_max_page_size(struct intel_memory_region 
>>>> **placements,
>>>> +                  unsigned int n_placements)
>>>>  {
>>>> -    u32 max_page_size = 0;
>>>> +    u32 max_page_size = I915_GTT_PAGE_SIZE_4K;
>>>>      int i;
>>>>      for (i = 0; i < n_placements; i++) {
>>>> @@ -28,7 +38,6 @@ static u32 object_max_page_size(struct 
>>>> intel_memory_region **placements,
>>>>          max_page_size = max_t(u32, max_page_size, mr->min_page_size);
>>>>      }
>>>> -    GEM_BUG_ON(!max_page_size);
>>>>      return max_page_size;
>>>>  }
>>>> @@ -99,7 +108,8 @@ __i915_gem_object_create_user_ext(struct 
>>>> drm_i915_private *i915, u64 size,
>>>>      i915_gem_flush_free_objects(i915);
>>>> -    size = round_up(size, object_max_page_size(placements, 
>>>> n_placements));
>>>> +    size = round_up(size, i915_gem_object_max_page_size(placements,
>>>> +                                n_placements));
>>>>      if (size == 0)
>>>>          return ERR_PTR(-EINVAL);
>>>
>>> Because of the changes above this path is now unreachable. I suppose 
>>> it was meant to tell the user "you have supplied no placements"? But 
>>> then GEM_BUG_ON (which you remove) used to be wrong.
>>>
>>
>> Yah, looks like an existing problem. May be this "size == 0" check
>> should have been made before we do the round_up()? ie., check input 
>> 'size'
>> paramter is not 0?
>> I think for now, I will remove this check as it was unreachable anyhow.
> 
> Hm that's true as well. i915_gem_create_ext_ioctl ensures at least one 
> placement and internal callers do as well.
> 
> To be safe, instead of removing maybe move to before "size = " and 
> change to "if (GEM_WARN_ON(n_placements == 0))"? Not sure.. Matt any 
> thoughts here given the changes in this patch?

The check is also to reject a zero sized object with args->size = 0, i.e 
round_up(0, PAGE_SIZE) == 0. So for sure that is still needed here.

> 
> Regards,
> 
> Tvrtko
> 
>>
>> Niranjana
>>
>>> Regards,
>>>
>>> Tvrtko
>>>
>>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h 
>>>> b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>>> index 7317d4102955..8c97bddad921 100644
>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>>> @@ -47,6 +47,8 @@ static inline bool i915_gem_object_size_2big(u64 
>>>> size)
>>>>  }
>>>>  void i915_gem_init__objects(struct drm_i915_private *i915);
>>>> +u32 i915_gem_object_max_page_size(struct intel_memory_region 
>>>> **placements,
>>>> +                  unsigned int n_placements);
>>>>  void i915_objects_module_exit(void);
>>>>  int i915_objects_module_init(void);