[Intel-gfx] [RFC PATCH i-g-t 1/1] tests/gem_mmap_offset: Exercise mapping to userptr

[Chris Wilson]

Quoting Janusz Krzysztofik (2020-01-31 13:12:34)
> Creating a mapping to a userptr backed GEM object may cause a currently
> unavoidable lockdep splat inside the i915 driver.  Then, such operation
> is expected to fail to prevent from that badness to happen.
> 
> Add a respective subtest for each mapping type.
> 
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  tests/i915/gem_mmap_offset.c | 55 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/tests/i915/gem_mmap_offset.c b/tests/i915/gem_mmap_offset.c
> index 7c4088cdf..a5f28328b 100644
> --- a/tests/i915/gem_mmap_offset.c
> +++ b/tests/i915/gem_mmap_offset.c
> @@ -141,6 +141,36 @@ static void bad_extensions(int i915)
>         gem_close(i915, arg.handle);
>  }
>  
> +static bool has_userptr(int i915)
> +{
> +       uint32_t handle = 0;
> +       void *ptr;
> +
> +       igt_assert_eq(posix_memalign(&ptr, 4096, 4096), 0);
> +       if (__gem_userptr(i915, ptr, 4096, 0, 0, &handle) == 0)
> +               gem_close(i915, handle);
> +       free(ptr);
> +
> +       return handle;
> +}
> +
> +static void userptr(int i915, uint64_t flags)
> +{
> +       struct drm_i915_gem_mmap_offset arg = {
> +               .flags = flags,
> +       };
> +       void *ptr;
> +
> +       igt_assert_eq(posix_memalign(&ptr, 4096, 4096), 0);
> +
> +       gem_userptr(i915, ptr, 4096, 0, 0, &arg.handle);
> +
> +       igt_assert_eq(mmap_offset_ioctl(i915, &arg), -EINVAL);

Not quite. The only reason it doesn't work is because the implementation
ties itself into knots, not that it is meant to not work. :|
-Chris