[igt-dev] [PATCH i-g-t 2/2] tests/i915-query: add new tests for perf configurations queries

[Lionel Landwerlin]

On 06/06/18 11:32, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2018-06-06 11:19:20)
>> On 05/06/18 19:47, Chris Wilson wrote:
>>> Quoting Lionel Landwerlin (2018-06-05 17:23:23)
>>>> +       len = ALIGN(query.oa.n_mux_regs * sizeof(uint32_t) * 2, 4096);
>>>> +       data = mmap(0, len, PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
>>>> +       memset(data, 0, len);
>>>> +       mprotect(data, len, PROT_READ);
>>>> +       query.oa.mux_regs_ptr = to_user_pointer(data);
>>>> +       igt_assert_eq(-EFAULT,
>>>> +                     query_perf_config_data(fd, sizeof(query), &query.query));
>>> Just the random thought, have we stuffed gem_mmap__gtt() addresses
>>> through these yet?
>>> -Chris
>>>
>> I don't understand why this would be an issue.
> It's a very easy way to be caught out with a lock inversion, as the
> kernel faults on the user provided GGTT address and calls into
> i915_gem_fault().
> -Chris
>
Just tried and it seems to work fine.
I'm not sure what you expected... Is it that if we take a lock on the 
device from the query api, then we deadlock?
If true that would be okay, because we're not taking a lock on that (yet).

-
Lionel