KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/include/rv/kunit.h b/include/rv/kunit.h
new file mode 100644
index 000000000..31e0b93c4
--- /dev/null
+++ b/include/rv/kunit.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2026-2029 Red Hat, Inc. Gabriele Monaco <gmonaco@redhat.com>
+ *
+ * Declaration of wrappers to allow mocking core functionality, like current,
+ * and other testing utilities.
+ * Necessary only when mocking may be needed. If the RV KUnit test is
+ * enabled, the wrappers incur an additional function call overhead.
+ */
+
+#ifndef _RV_KUNIT_H
+#define _RV_KUNIT_H
+
+#if IS_ENABLED(CONFIG_RV_MONITORS_KUNIT_TEST)
+
+#include <kunit/test.h>
+#include <kunit/test-bug.h>
+#include <linux/delay.h>
+
+int rv_set_testing(struct kunit_suite *suite);
+void rv_clear_testing(struct kunit_suite *suite);
+
+#define RV_KUNIT_MAX_MOCK_TASKS 8
+
+struct rv_kunit_ctx {
+	int reactions, expected;
+	int mock_task_count;
+	struct task_struct *mock_tasks[RV_KUNIT_MAX_MOCK_TASKS];
+};
+
+#define RV_KUNIT_EXPECT_REACTION(test, ctx)                             \
+	do {                                                            \
+		KUNIT_EXPECT_EQ(test, ctx->reactions, ++ctx->expected); \
+		if (ctx->reactions != ctx->expected)                    \
+			ctx->expected = ctx->reactions;                 \
+	} while (0)
+
+#define RV_KUNIT_EXPECT_NO_REACTION(test, ctx)                        \
+	do {                                                          \
+		KUNIT_EXPECT_EQ(test, ctx->reactions, ctx->expected); \
+		if (ctx->reactions != ctx->expected)                  \
+			ctx->expected = ctx->reactions;               \
+	} while (0)
+
+#define RV_KUNIT_EXPECT_REACTION_HERE(test, ctx)                             \
+	for (int __done = ({ RV_KUNIT_EXPECT_NO_REACTION(test, ctx); 0; });  \
+	     !__done;                                                        \
+	     __done = ({ RV_KUNIT_EXPECT_REACTION(test, ctx); 1; }))
+
+struct rv_kunit_mon {
+	struct rv_monitor *rv_this;
+	int (*monitor_init)(void);
+	void (*monitor_destroy)(void);
+	bool is_per_task;
+	int *task_slot;
+	void (*task_reset)(struct task_struct *task);
+};
+
+void prepare_test(struct kunit *test, const struct rv_kunit_mon *mon);
+void teardown_test(void *arg);
+struct task_struct *rv_kunit_alloc_mock_task(struct kunit *test);
+
+void rv_mock_current(struct task_struct *tsk);
+struct task_struct *rv_get_mock_current(void);
+
+#define rv_get_current() (unlikely(kunit_get_current_test()) ? rv_get_mock_current() : current)
+
+#else /* !CONFIG_RV_MONITORS_KUNIT_TEST */
+
+#define rv_get_current() current
+
+#endif /* CONFIG_RV_MONITORS_KUNIT_TEST */
+#endif /* _RV_KUNIT_H */