[igt-dev] [RFC 5/5] igt/lib: If mappable aperture is missing return 0 size

[Antonio Argenziano]

On 21/02/19 13:51, Chris Wilson wrote:
> Quoting Antonio Argenziano (2019-02-21 21:45:46)
>>
>>
>> On 21/02/19 12:01, Chris Wilson wrote:
>>> Quoting Antonio Argenziano (2019-02-21 19:27:45)
>>>> So far the aperture size has been read directly from the bar,
>>>> in this patch we return zero if the mappable aperture is not available
>>>> as the value stored in the bar might not be accurate. The patch also adds a
>>>> 'require' when a call to gem_mappable_aperture_size() is made so that
>>>> the aperture is guaranteed to exist before checking the size.
>>>>
>>>> Cc: Katarzyna Dec <katarzyna.dec at intel.com>
>>>> Cc: Chris Wilson <chris at chris-wilson.co.uk>
>>>> Cc: Matthew Auld <matthew.auld at intel.com>
>>>> Signed-off-by: Antonio Argenziano <antonio.argenziano at intel.com>
>>>> ---
>>>>    lib/ioctl_wrappers.c            | 28 +++++++++++++++++++---------
>>>>    lib/ioctl_wrappers.h            |  2 +-
>>>>    tests/i915/gem_concurrent_all.c | 12 ++++++------
>>>>    tests/i915/gem_cpu_reloc.c      | 14 ++++++++++----
>>>>    tests/i915/gem_mmap.c           |  4 ++--
>>>>    tests/i915/gem_mmap_gtt.c       | 10 +++++-----
>>>>    tests/i915/gem_pwrite.c         |  4 ++--
>>>>    tests/i915/gem_shrink.c         |  2 +-
>>>>    tests/i915/i915_pm_rpm.c        |  2 +-
>>>>    tests/kms_flip.c                |  2 +-
>>>>    tests/prime_mmap.c              |  7 +++++--
>>>>    11 files changed, 53 insertions(+), 34 deletions(-)
>>>>
>>>> diff --git a/lib/ioctl_wrappers.c b/lib/ioctl_wrappers.c
>>>> index 25dd8ad3..ab7c7a5e 100644
>>>> --- a/lib/ioctl_wrappers.c
>>>> +++ b/lib/ioctl_wrappers.c
>>>> @@ -1440,19 +1440,14 @@ uint64_t gem_aperture_size(int fd)
>>>>           return aperture_size;
>>>>    }
>>>>    
>>>> -/**
>>>> - * gem_mappable_aperture_size:
>>>> - *
>>>> - * Feature test macro to query the kernel for the mappable gpu aperture size.
>>>> - * This is the area available for GTT memory mappings.
>>>> - *
>>>> - * Returns: The mappable gtt address space size.
>>>> - */
>>>> -uint64_t gem_mappable_aperture_size(void)
>>>> +static uint64_t __gem_mappable_aperture_size(int fd)
>>>>    {
>>>>           struct pci_device *pci_dev = intel_get_pci_device();
>>>>           int bar;
>>>>    
>>>> +       if (!gem_mmap__has_gtt(fd))
>>>> +               return 0; /* Aperture not available */
>>>> +
>>>>           if (intel_gen(pci_dev->device_id) < 3)
>>>>                   bar = 0;
>>>
>>> I swear we made this accessible via fd so that we didn't need root to
>>> poke around libpciacess.
>>
>> mhh, couldn't find it. Is it in some IOCTL?
> 
> No, we extended get_aperture_ioctl to provide it, once upon a time. I
> suggest we do something similar, or we use a param to get the actual
> value. (Even if it's legacy, we can still justify a usecase as I'm
> pretty sure 256MiB is hardcoded into several legacy userspaces.)

Is something like: https://paste.debian.net/1072096/ acceptable?

Antonio

> -Chris
>