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

[Chris Wilson]

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.)
-Chris