Re: [igt-dev] [PATCH i-g-t v21 20/35] tests/api_intel_bb: Add subtest to check render batch on the last page

On Fri, Mar 05, 2021 at 02:45:07PM +0000, Chris Wilson wrote:

Quoting Zbigniew Kempczyński (2021-03-01 16:13:48)

quoted

Last page (on 48-bit ppgtt) seems to be problematic when full
3D pipeline batch is inserted and executed from it. Try to find out
which generations are still prone to hang on it.

Signed-off-by: Zbigniew Kempczyński <redacted>
Cc: Chris Wilson <redacted>
---
 tests/i915/api_intel_bb.c | 74 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/tests/i915/api_intel_bb.c b/tests/i915/api_intel_bb.c
index d5ed77314..207a70fab 100644
--- a/tests/i915/api_intel_bb.c
+++ b/tests/i915/api_intel_bb.c

@@ -36,6 +36,7 @@
 #include <glib.h>
 #include <zlib.h>
 #include "intel_bufops.h"
+#include "sw_sync.h"
 
 #define PAGE_SIZE 4096
 

@@ -1391,6 +1392,76 @@ static void render_ccs(struct buf_ops *bops)
        igt_assert_f(fails == 0, "render-ccs fails: %d\n", fails);
 }
 
+static void last_page(struct buf_ops *bops, uint32_t width, uint32_t height)
+{
+       struct intel_bb *ibb1, *ibb2;
+       struct intel_buf src, dst;
+       int i915 = buf_ops_get_fd(bops);
+       uint32_t devid = intel_get_drm_devid(i915);
+       igt_render_copyfunc_t render_copy = NULL;
+       uint64_t gtt_size;
+       uint64_t ctx;
+       int ret;
+
+       igt_require(gem_uses_full_ppgtt(i915));
+       gtt_size = gem_aperture_size(i915);
+
+       ctx = gem_context_create(i915);
+
+       ibb1 = intel_bb_create_full(i915, ctx, PAGE_SIZE,
+                                  0, gtt_size, INTEL_ALLOCATOR_SIMPLE,
+                                  ALLOC_STRATEGY_LOW_TO_HIGH);
+
+       ibb2 = intel_bb_create_full(i915, 0, PAGE_SIZE,
+                                  0, gtt_size, INTEL_ALLOCATOR_SIMPLE,
+                                  ALLOC_STRATEGY_HIGH_TO_LOW);
+
+       if (debug_bb) {
+               intel_bb_set_debug(ibb1, true);
+               intel_bb_set_debug(ibb2, true);
+       }
+
+       scratch_buf_init(bops, &src, width, height, I915_TILING_NONE,
+                        I915_COMPRESSION_NONE);
+       scratch_buf_init(bops, &dst, width, height, I915_TILING_NONE,
+                        I915_COMPRESSION_NONE);
+       scratch_buf_draw_pattern(bops, &src,
+                                0, 0, width, height,
+                                0, 0, width, height, 0);
+
+       render_copy = igt_get_render_copyfunc(devid);
+       igt_assert(render_copy);
+
+       render_copy(ibb1,
+                   &src,
+                   0, 0, width, height,
+                   &dst,
+                   0, 0);
+       gem_sync(i915, dst.handle);
+       igt_assert(sync_fence_status(ibb1->fence) == 1);

If you don't want to mix apis, then
s/gem_sync/sync_fence_wait(ibb1->fence, -1));

Also igt_assert_eq(sync_fence_status(ibb1->fence), 1));

Ok, I'll use sync_fence_wait().

quoted

+       intel_bb_destroy(ibb1);
+
+       intel_buf_close(bops, &dst);
+       scratch_buf_init(bops, &dst, width, height, I915_TILING_NONE,
+                        I915_COMPRESSION_NONE);
+
+       render_copy(ibb2,
+                   &src,
+                   0, 0, width, height,
+                   &dst,
+                   0, 0);
+
+       /* We likely got a hang here, so free resources before assert */
+       gem_sync(i915, dst.handle);
+       ret = sync_fence_status(ibb2->fence);
+
+       intel_bb_destroy(ibb2);
+       intel_buf_close(bops, &src);
+       intel_buf_close(bops, &dst);
+
+       igt_assert_f(ret == 1, "Batch in last page in rcs leads to hang\n");

Now I always thought that the position of the state inside the last half
of the rendercopy batch page would provide sufficient padding to prevent
the prefetch from crossing the domain boundary.

If you want to push the test further you would move the aux buffers out
of the batch page and use execbuf.batch_start_offset to position the
batch at the very end of the page (and possibly a binary search therein
to find the failure position).
-Chris

This is not easy task. 3d pipeline built for rendercopy has hard assumptions
(split 2KB code + 2KB aux data). So we have to change rendercopy pipelines
to allow code + aux separation. I don't think then fail in last page should
be part of allocator series. We exposed the problem there and for allocator
IMO that's enough to limit the ppgtt space.

--
Zbigniew
 
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