drm/xe/rtp: Don't short-circuit to false in or-yes case

While RTP processing evaluates true on the "yes-or" case (i.e. a
conjunction of rules that evaluate to true followed by an "OR" without
the right hand operand), it does not on the "or-yes" one.

Both cases are considered malformed and could be a result of someone
dropping checks deemed not necessary anymore and forgetting to drop the
superfluous "OR".  Nevertheless, we should aim for consistency, and
having the "or-yes" case also evaluating to true while also causing a
warning seems reasonable.  So let's do that.

The "or-yes" pattern being evaluated to false comes from the fact that
that we unconditionally short-circuit upon finding XE_RTP_MATCH_OR on
the outer loop.  We should only do that if the preceding conjunction of
rules evaluated to true (meaning that rcount must be non-zero) and
continue the evaluation otherwise.

Do that and also add extra test cases to validate the short-circuiting
behavior.

Notice that some of the new test cases have a "FIXME" comment, which
comes from the fact that we are unable to detect syntax errors after the
short-circuit point.  That is going to be fixed in a follow-up change.

Link: https://lore.kernel.org/intel-xe/871pfw4lo9.fsf@intel.com/
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Violet Monti <violet.monti@intel.com>
Link: https://patch.msgid.link/20260522-rtp-rule-parser-v3-3-0c51039899f4@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/gpu/drm/xe/xe_rtp.c b/drivers/gpu/drm/xe/xe_rtp.c
index 0e1adf07e4e7..299fa4209a26 100644
--- a/drivers/gpu/drm/xe/xe_rtp.c
+++ b/drivers/gpu/drm/xe/xe_rtp.c
@@ -47,12 +47,18 @@ static bool rule_matches_with_err(const struct xe_device *xe,
 	for (r = rules, i = 0; i < n_rules; r = &rules[++i]) {
 		switch (r->match_type) {
 		case XE_RTP_MATCH_OR:
+			if (drm_WARN_ON(&xe->drm, !rcount)) {
+				if (err)
+					*err = -EINVAL;
+				continue;
+			}
+
 			/*
-			 * This is only reached if a complete set of
-			 * rules passed or none were evaluated. For both cases,
-			 * shortcut the other rules and return the proper value.
+			 * This is only reached if a complete conjunction of
+			 * rules passed, in which case we shortcut the other
+			 * rules and return true.
 			 */
-			goto done;
+			return true;
 		case XE_RTP_MATCH_PLATFORM:
 			match = xe->info.platform == r->platform;
 			break;
@@ -169,7 +175,6 @@ static bool rule_matches_with_err(const struct xe_device *xe,
 		}
 	}
 
-done:
 	if (drm_WARN_ON(&xe->drm, !rcount))
 		goto error;