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

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 22/09/2022 17:18, Matthew Auld wrote:
> 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.

Oh yeah sneaky round up.. Thanks, my bad.

Regards,

Tvrtko