drm/i915/perf: Consider OA buffer boundary when zeroing out reports

For reports that are not powers of 2, reports at the end of the OA
buffer may get split across the buffer boundary. When zeroing out such
reports, take the split into consideration.

v2: Use OA_BUFFER_SIZE (Ashutosh)

Fixes: 09a3601 ("drm/i915/perf: Clear out entire reports after reading if not power of 2 size")
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230616173402.699776-1-umesh.nerlige.ramappa@intel.com

Author: unerlige

drivers/gpu/drm/i915/i915_perf.c

@@ -868,8 +868,17 @@ static int gen8_append_oa_reports(struct i915_perf_stream *stream,
 			oa_report_id_clear(stream, report32);
 			oa_timestamp_clear(stream, report32);
 		} else {
+			u8 *oa_buf_end = stream->oa_buffer.vaddr +
+					 OA_BUFFER_SIZE;
+			u32 part = oa_buf_end - (u8 *)report32;
+
 			/* Zero out the entire report */
-			memset(report32, 0, report_size);
+			if (report_size <= part) {
+				memset(report32, 0, report_size);
+			} else {
+				memset(report32, 0, part);
+				memset(oa_buf_base, 0, report_size - part);
+			}
 		}
 	}