i915/gem_exec_(fence|schedule): Use WC mmaps

Since we are hiding our write hazards, gem_read() may not know if it
needs to flush the CPU caches prior to reading back. As we lie to the
kernel, use an explicit WC mmap for result readback.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1875
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 12 insertions, 8 deletions

diff --git a/tests/i915/gem_exec_fence.c b/tests/i915/gem_exec_fence.c
index 20ff2535..4140bff2 100644
--- a/tests/i915/gem_exec_fence.c
+++ b/tests/i915/gem_exec_fence.c
@@ -455,10 +455,12 @@ static void test_submit_fence(int i915, unsigned int engine)
 			.buffers_ptr = to_user_pointer(&obj),
 			.buffer_count = 1,
 		};
-		uint32_t result;
+		uint32_t *result;
 		int out;
 
 		obj.handle = timeslicing_batches(i915, &offset);
+		result = gem_mmap__device_coherent(i915, obj.handle,
+						   0, 4096, PROT_READ);
 
 		execbuf.flags = engine | I915_EXEC_FENCE_OUT;
 		execbuf.batch_start_offset = 0;
@@ -473,6 +475,7 @@ static void test_submit_fence(int i915, unsigned int engine)
 		gem_context_destroy(i915, execbuf.rsvd1);
 
 		gem_sync(i915, obj.handle);
+		gem_close(i915, obj.handle);
 
 		/* no hangs! */
 		out = execbuf.rsvd2;
@@ -483,9 +486,8 @@ static void test_submit_fence(int i915, unsigned int engine)
 		igt_assert_eq(sync_fence_status(out), 1);
 		close(out);
 
-		gem_read(i915, obj.handle, 4000, &result, sizeof(result));
-		igt_assert_eq(result, 16);
-		gem_close(i915, obj.handle);
+		igt_assert_eq(result[1000], 16);
+		munmap(result, 4096);
 	}
 }
 
@@ -528,6 +530,7 @@ static uint32_t submitN_batches(int i915, uint32_t offset, int count)
 static void test_submitN(int i915, unsigned int engine, int count)
 {
 	unsigned int offset = 24 << 20;
+	unsigned int sz = ALIGN((count + 1) * 1024, 4096);
 	struct drm_i915_gem_exec_object2 obj = {
 		.handle = submitN_batches(i915, offset, count),
 		.offset = offset,
@@ -538,8 +541,9 @@ static void test_submitN(int i915, unsigned int engine, int count)
 		.buffer_count = 1,
 		.flags = engine | I915_EXEC_FENCE_OUT,
 	};
+	uint32_t *result =
+		gem_mmap__device_coherent(i915, obj.handle, 0, sz, PROT_READ);
 	int fence[count];
-	uint32_t result;
 
 	igt_require(gem_scheduler_has_semaphores(i915));
 	igt_require(gem_scheduler_has_preemption(i915));
@@ -557,6 +561,7 @@ static void test_submitN(int i915, unsigned int engine, int count)
 	}
 
 	gem_sync(i915, obj.handle);
+	gem_close(i915, obj.handle);
 
 	/* no hangs! */
 	for (int i = 0; i < count; i++) {
@@ -564,9 +569,8 @@ static void test_submitN(int i915, unsigned int engine, int count)
 		close(fence[i]);
 	}
 
-	gem_read(i915, obj.handle, 0, &result, sizeof(result));
-	igt_assert_eq(result, 8 * count);
-	gem_close(i915, obj.handle);
+	igt_assert_eq(*result, 8 * count);
+	munmap(result, sz);
 }
 
 static void alarm_handler(int sig)