[igt-dev] [PATCH 03/29] i915/perf: Fix OA short_reads test

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

With 5000 ns oa exponent, report lost errors can occur. A report lost
header can be read by the user even when there are no valid OA report
samples, so we get an 8 byte read. This defeats the EFAULT check.

When checking for EFAULT on a sampled report, discard any report lost
errors.

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
---
 tests/i915/perf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/i915/perf.c b/tests/i915/perf.c
index 51e2dc87..0b8f6ac8 100644
--- a/tests/i915/perf.c
+++ b/tests/i915/perf.c
@@ -2853,8 +2853,13 @@ test_short_reads(void)
 
 	/* A read that can't return a single record because it would result
 	 * in a fault on buffer overrun should result in an EFAULT error...
+	 *
+	 * Make sure to weed out all report lost errors before verifying EFAULT.
 	 */
-	ret = read(stream_fd, pages + page_size - 16, page_size);
+	header = (void *)(pages + page_size - 16);
+	do {
+		ret = read(stream_fd, header, page_size);
+	} while (ret > 0 && header->type == DRM_I915_PERF_RECORD_OA_REPORT_LOST);
 	igt_assert_eq(ret, -1);
 	igt_assert_eq(errno, EFAULT);
 
-- 
2.25.1