Re: [igt-dev] [RFT i-g-t] lib/i915: Assert mmap size alignment

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

On 05/03/2019 08:38, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-03-05 07:55:43)
>>
>> On 04/03/2019 14:45, Chris Wilson wrote:
>>> Quoting Tvrtko Ursulin (2019-03-04 14:11:31)
>>>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>>
>>>> Fishing for fails...
>>>>
>>>> /*
>>>> mmap(2) mandates size is page aligned so check this in our wrappers.
>>>> */
>>>>
>>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>> ---
>>>>    lib/i915/gem_mman.c |  4 ++++
>>>>    lib/igt_fb.c        | 14 ++++++++------
>>>>    tests/kms_ccs.c     | 14 ++++++++------
>>>>    tests/kms_psr.c     |  8 ++++----
>>>>    4 files changed, 24 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/lib/i915/gem_mman.c b/lib/i915/gem_mman.c
>>>> index 3cf9a6bbdb31..084dbb3b3678 100644
>>>> --- a/lib/i915/gem_mman.c
>>>> +++ b/lib/i915/gem_mman.c
>>>> @@ -57,6 +57,8 @@ void *__gem_mmap__gtt(int fd, uint32_t handle, uint64_t size, unsigned prot)
>>>>           struct drm_i915_gem_mmap_gtt mmap_arg;
>>>>           void *ptr;
>>>>    
>>>> +       igt_assert(!(size & 4095));
>>>
>>> Fwiw, it's probably best if we had some kind of IGT_BUG_ON() that caused
>>> a much more visible explosion than a mere test failure.
>>>
>>> #define IGT_BUG_ON(cond) if (!(cond)) raise(SIGILL)
>>
>> No idea if that would be worthwhile.
>>
>> But anyway, it seems I have identified all the tests which do
>> non-page-aligned mmap. So..
>>
>> a) leave the assert in low level mmap helpers
>> b) move the assert to higher level wrappers
>> c) round up in wrappers is not an option due unmap
>> d) do nothing in igt
> 
> Imo leave the wrappers alone, fix the bugs in the callers, fume that it
> didn't explode earlier.

Not even a small igt_warn or tiny igt_debug in the wrappers? :)

Regards,

Tvrtko
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