[Intel-gfx] [PATCH] drm/i915: Use fault-injection to force the shrinker to run in live GTT tests

[Chris Wilson]

On Fri, Feb 10, 2017 at 03:46:52PM +0000, Matthew Auld wrote:
> On 8 February 2017 at 11:40, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > It is possible whilst allocating the page-directory tree for a ppgtt
> > bind that the shrinker may run and reap unused parts of the tree. If the
> > shrinker happens to remove a chunk of the tree that the
> > allocate_va_range has already processed, we may then try to insert into
> > the dangling tree. This test uses the fault-injection framework to force
> > the shrinker to be invoked before we allocate new pages, i.e. new chunks
> > of the PD tree.
> >
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=99295
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/Kconfig.debug            |  1 +
> >  drivers/gpu/drm/i915/i915_drv.h               |  2 +
> >  drivers/gpu/drm/i915/i915_gem_gtt.c           |  6 ++
> >  drivers/gpu/drm/i915/i915_selftest.h          |  2 +
> >  drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 98 +++++++++++++++++++++++++++
> >  5 files changed, 109 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
> > index a4d8cfd77c3c..68ff072f8b76 100644
> > --- a/drivers/gpu/drm/i915/Kconfig.debug
> > +++ b/drivers/gpu/drm/i915/Kconfig.debug
> > @@ -65,6 +65,7 @@ config DRM_I915_SELFTEST
> >         bool "Enable selftests upon driver load"
> >         depends on DRM_I915
> >         default n
> > +       select FAULT_INJECTION
> >         select PRIME_NUMBERS
> >         help
> >           Choose this option to allow the driver to perform selftests upon
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 56a3de94ecf4..f298da9eaebc 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2468,6 +2468,8 @@ struct drm_i915_private {
> >                 int     irq;
> >         } lpe_audio;
> >
> > +       I915_SELFTEST_DECLARE(struct fault_attr vm_fault);
> > +
> >         /*
> >          * NOTE: This is the dri1/ums dungeon, don't add stuff here. Your patch
> >          * will be rejected. Instead look for a better place.
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 36142d3d99d2..0247b26265dd 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -23,6 +23,9 @@
> >   *
> >   */
> >
> > +#include <linux/slab.h> /* fault-inject.h is not standalone! */
> What do you mean by not standalone, it doesn't build without this?

Yup. fault-inject.h pulls in a few types, most notably struct kmem_cache
without a forward declaration. That needs fixing, but for now an include
allows us to build.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre