Using a clear page for scratch means that we have relatively benign errors in case it is accidentally used, but that can be rather too benign for debugging. If we poison the scratch, ideally it quickly results in an obvious error.
Suggested-by: Mika Kuoppala <[email protected]> Signed-off-by: Chris Wilson <[email protected]> Cc: Mika Kuoppala <[email protected]> --- drivers/gpu/drm/i915/gt/intel_gtt.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c index 45d8e0019a8e..aaba06a774ab 100644 --- a/drivers/gpu/drm/i915/gt/intel_gtt.c +++ b/drivers/gpu/drm/i915/gt/intel_gtt.c @@ -331,6 +331,21 @@ int setup_scratch_page(struct i915_address_space *vm, gfp_t gfp) if (unlikely(!page)) goto skip; + /* + * Use a non-zero scratch page for debugging. + * + * We want a value that should be reasonably obvious + * to spot in the error state, while also causing a GPU hang + * if executed. We prefer using a clear page in production, so + * should it ever be accidentally used, the effect should be + * fairly benign. + */ + if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)) { + kunmap_atomic(memset64(kmap_atomic(page), + POISON_FREE, + size / sizeof(64))); + } + addr = dma_map_page_attrs(vm->dma, page, 0, size, PCI_DMA_BIDIRECTIONAL, -- 2.25.0 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
