pkg/bisect: try to drop instrumentation

Refactor Minimize().

As a part of Minimize(), attempt to drop all unnecessary instrumentation
and test whether the kernel is still crashing.

This should reduce the number of irrelevant crashes during bisection and
thus increase bisection result quality.

1 files changed, 13 insertions, 10 deletions

diff --git a/pkg/bisect/bisect.go b/pkg/bisect/bisect.go
index 815d6ba72..3d3de92b6 100644
--- a/pkg/bisect/bisect.go
+++ b/pkg/bisect/bisect.go
@@ -260,14 +260,14 @@ func (env *env) bisect() (*Result, error) {
 	}
 	env.reportTypes = testRes.types
 
-	if len(cfg.Kernel.BaselineConfig) != 0 {
-		testRes1, err := env.minimizeConfig()
-		if err != nil {
-			return nil, err
-		}
-		if testRes1 != nil {
-			testRes = testRes1
-		}
+	testRes1, err := env.minimizeConfig()
+	if err != nil {
+		return nil, fmt.Errorf("config minimization failed: %w", err)
+	}
+	if testRes1 != nil {
+		// If config minimization even partially succeeds, minimizeConfig()
+		// would return a non-nil value of a new report.
+		testRes = testRes1
 	}
 
 	bad, good, results1, fatalResult, err := env.commitRange()
@@ -372,11 +372,14 @@ func (env *env) minimizeConfig() (*testResult, error) {
 		if err != nil {
 			return 0, err
 		}
-		testResults[hash.Hash(test)] = testRes
+		if testRes.verdict == vcs.BisectBad {
+			// Only remember crashes.
+			testResults[hash.Hash(test)] = testRes
+		}
 		return testRes.verdict, err
 	}
 	minConfig, err := env.minimizer.Minimize(env.cfg.Manager.SysTarget, env.cfg.Kernel.Config,
-		env.cfg.Kernel.BaselineConfig, env.cfg.Trace, predMinimize)
+		env.cfg.Kernel.BaselineConfig, env.reportTypes, env.cfg.Trace, predMinimize)
 	if err != nil {
 		return nil, err
 	}