+ mm-add-basic-tests-for-lazy_mmu.patch added to mm-new branch

+ mm-add-basic-tests-for-lazy_mmu.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: add basic tests for lazy_mmu
has been added to the -mm mm-new branch.  Its filename is
     mm-add-basic-tests-for-lazy_mmu.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-basic-tests-for-lazy_mmu.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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fixup patches in mm-new.

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------------------------------------------------------
From: Kevin Brodsky <kevin.brodsky@arm.com>
Subject: mm: add basic tests for lazy_mmu
Date: Mon, 15 Dec 2025 15:03:23 +0000

Add basic KUnit tests for the generic aspects of the lazy MMU mode: ensure
that it appears active when it should, depending on how enable/disable and
pause/resume pairs are nested.

Link: https://lkml.kernel.org/r/20251215150323.2218608-15-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Juegren Gross <jgross@suse.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/Kconfig                     |   12 +++++
 mm/Makefile                    |    1 
 mm/tests/lazy_mmu_mode_kunit.c |   71 +++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)

--- a/mm/Kconfig~mm-add-basic-tests-for-lazy_mmu
+++ a/mm/Kconfig
@@ -1471,6 +1471,18 @@ config ARCH_HAS_LAZY_MMU_MODE
 	  MMU-related architectural state to be deferred until the mode is
 	  exited. See <linux/pgtable.h> for details.
 
+config LAZY_MMU_MODE_KUNIT_TEST
+	tristate "KUnit tests for the lazy MMU mode" if !KUNIT_ALL_TESTS
+	depends on ARCH_HAS_LAZY_MMU_MODE
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Enable this option to check that the lazy MMU mode interface behaves
+	  as expected. Only tests for the generic interface are included (not
+	  architecture-specific behaviours).
+
+	  If unsure, say N.
+
 source "mm/damon/Kconfig"
 
 endmenu
--- a/mm/Makefile~mm-add-basic-tests-for-lazy_mmu
+++ a/mm/Makefile
@@ -147,3 +147,4 @@ obj-$(CONFIG_SHRINKER_DEBUG) += shrinker
 obj-$(CONFIG_EXECMEM) += execmem.o
 obj-$(CONFIG_TMPFS_QUOTA) += shmem_quota.o
 obj-$(CONFIG_PT_RECLAIM) += pt_reclaim.o
+obj-$(CONFIG_LAZY_MMU_MODE_KUNIT_TEST) += tests/lazy_mmu_mode_kunit.o
diff --git a/mm/tests/lazy_mmu_mode_kunit.c a/mm/tests/lazy_mmu_mode_kunit.c
new file mode 100644
--- /dev/null
+++ a/mm/tests/lazy_mmu_mode_kunit.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+#include <linux/pgtable.h>
+
+static void expect_not_active(struct kunit *test)
+{
+	KUNIT_EXPECT_FALSE(test, is_lazy_mmu_mode_active());
+}
+
+static void expect_active(struct kunit *test)
+{
+	KUNIT_EXPECT_TRUE(test, is_lazy_mmu_mode_active());
+}
+
+static void lazy_mmu_mode_active(struct kunit *test)
+{
+	expect_not_active(test);
+
+	lazy_mmu_mode_enable();
+	expect_active(test);
+
+	{
+		/* Nested section */
+		lazy_mmu_mode_enable();
+		expect_active(test);
+
+		lazy_mmu_mode_disable();
+		expect_active(test);
+	}
+
+	{
+		/* Paused section */
+		lazy_mmu_mode_pause();
+		expect_not_active(test);
+
+		{
+			/* No effect (paused) */
+			lazy_mmu_mode_enable();
+			expect_not_active(test);
+
+			lazy_mmu_mode_disable();
+			expect_not_active(test);
+
+			lazy_mmu_mode_pause();
+			expect_not_active(test);
+
+			lazy_mmu_mode_resume();
+			expect_not_active(test);
+		}
+
+		lazy_mmu_mode_resume();
+		expect_active(test);
+	}
+
+	lazy_mmu_mode_disable();
+	expect_not_active(test);
+}
+
+static struct kunit_case lazy_mmu_mode_test_cases[] = {
+	KUNIT_CASE(lazy_mmu_mode_active),
+	{}
+};
+
+static struct kunit_suite lazy_mmu_mode_test_suite = {
+	.name = "lazy_mmu_mode",
+	.test_cases = lazy_mmu_mode_test_cases,
+};
+kunit_test_suite(lazy_mmu_mode_test_suite);
+
+MODULE_DESCRIPTION("Tests for the lazy MMU mode");
+MODULE_LICENSE("GPL");
_

Patches currently in -mm which might be from kevin.brodsky@arm.com are

x86-xen-simplify-flush_lazy_mmu.patch
powerpc-mm-implement-arch_flush_lazy_mmu_mode.patch
sparc-mm-implement-arch_flush_lazy_mmu_mode.patch
mm-clarify-lazy_mmu-sleeping-constraints.patch
mm-introduce-config_arch_has_lazy_mmu_mode.patch
mm-introduce-generic-lazy_mmu-helpers.patch
mm-bail-out-of-lazy_mmu_mode_-in-interrupt-context.patch
mm-enable-lazy_mmu-sections-to-nest.patch
arm64-mm-replace-tif_lazy_mmu-with-is_lazy_mmu_mode_active.patch
powerpc-mm-replace-batch-active-with-is_lazy_mmu_mode_active.patch
sparc-mm-replace-batch-active-with-is_lazy_mmu_mode_active.patch
x86-xen-use-lazy_mmu_state-when-context-switching.patch
mm-add-basic-tests-for-lazy_mmu.patch