drm/i915/gtt: Pin vma during virtual address allocation

Dynamic page table allocation might wake the shrinker
when memory is requested for page table structures.
As this happens when we try to allocate the virtual address
during binding, our vma might be among the targets for eviction.
We should do i915_vma_pin() and do pin early in there like Chris
suggests but this is interim solution.

Shield our vma from shrinker by incrementing pin count before
the virtual address is allocated.

The proper place to fix this would be in gem, inside of
i915_vma_pin(). But we don't have that yet so take the short
cut as a intermediate solution.

Testcase: igt/gem_ctx_thrash
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 0cc0cf4362eae975022b2dadab66d67c94a83beb..29d76b06e7de6b063e209c4e50b8a452792d980f 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2870,9 +2870,12 @@ int i915_vma_bind(struct i915_vma *vma, enum i915_cache_level cache_level,
                                    vma->node.size,
                                    VM_TO_TRACE_NAME(vma->vm));
 
+               /* XXX: i915_vma_pin() will fix this +- hack */
+               vma->pin_count++;
                ret = vma->vm->allocate_va_range(vma->vm,
                                                 vma->node.start,
                                                 vma->node.size);
+               vma->pin_count--;
                if (ret)
                        return ret;
        }