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, 57 insertions, 0 deletions

diff --git a/tools/testing/vma/main.c b/tools/testing/vma/main.c
new file mode 100644
index 000000000..18338f5d2
--- /dev/null
+++ b/tools/testing/vma/main.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "shared.h"
+/*
+ * Directly import the VMA implementation here. Our vma_internal.h wrapper
+ * provides userland-equivalent functionality for everything vma.c uses.
+ */
+#include "../../../mm/vma_init.c"
+#include "../../../mm/vma_exec.c"
+#include "../../../mm/vma.c"
+
+/* Tests are included directly so they can test static functions in mm/vma.c. */
+#include "tests/merge.c"
+#include "tests/mmap.c"
+#include "tests/vma.c"
+
+int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
+
+/* Helper functions which utilise static kernel functions. */
+
+struct vm_area_struct *merge_existing(struct vma_merge_struct *vmg)
+{
+	struct vm_area_struct *vma;
+
+	vma = vma_merge_existing_range(vmg);
+	if (vma)
+		vma_assert_attached(vma);
+	return vma;
+}
+
+int attach_vma(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	int res;
+
+	res = vma_link(mm, vma);
+	if (!res)
+		vma_assert_attached(vma);
+	return res;
+}
+
+/* Main test running which invokes tests/ *.c runners. */
+int main(void)
+{
+	int num_tests = 0, num_fail = 0;
+
+	maple_tree_init();
+	vma_state_init();
+
+	run_merge_tests(&num_tests, &num_fail);
+	run_mmap_tests(&num_tests, &num_fail);
+	run_vma_tests(&num_tests, &num_fail);
+
+	printf("%d tests run, %d passed, %d failed.\n",
+	       num_tests, num_tests - num_fail, num_fail);
+
+	return num_fail == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}