selftests/mm: add a GUP selftest

Add a new GUP selftest which uses kselftest_harness.h.  Cover 12 mapping
configurations: THP enabled, THP disabled and HugeTLB, each across
private/shared mappings and with/without FOLL_WRITE.  Run 5 test cases for
every variant: get_user_pages, get_user_pages_fast, pin_user_pages,
pin_user_pages_fast and pin_user_pages_longterm.

Use two default hugeTLB pages and derive the mapping size from their size.
This exercises GUP both within a single HugeTLB page and across a HugeTLB
boundary, without reserving an excessive number of pages.

Sweep four nr_pages_per_call values for each test: 1, 512, 123 and all
pages.  This preserves the coverage previously provided by
run_gup_matrix(): 12 mapping combinations x 5 GUP/PUP operations x 4 batch
sizes.  In total the selftest reports 60 TAP cases and issues 240 ioctls.

Do not carry DUMP_USER_PAGES_TEST into the new selftest because its output
is written to the kernel log and the selftest does not verify that output.

Add the new gup binary to the selftests/mm build, run_vmtests.sh and
MAINTAINERS.  Update mm/Kconfig to describe the benchmark and selftest
split.

Link: https://lore.kernel.org/20260918112234.195857-7-sarthak.sharma@arm.com
Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>

3 files changed, 264 insertions, 0 deletions

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index d6337156111a..7d69baeb93f4 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -58,6 +58,7 @@ endif
 
 TEST_GEN_FILES = cow
 TEST_GEN_FILES += compaction_test
+TEST_GEN_FILES += gup
 TEST_GEN_FILES += gup_longterm
 TEST_GEN_FILES += hmm-tests
 TEST_GEN_FILES += hugetlb-madvise
diff --git a/tools/testing/selftests/mm/gup.c b/tools/testing/selftests/mm/gup.c
new file mode 100644
index 000000000000..a6a8ca47d12e
--- /dev/null
+++ b/tools/testing/selftests/mm/gup.c
@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0
+#define __SANE_USERSPACE_TYPES__ // Use ll64
+#include <fcntl.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <mm/gup_test.h>
+#include "vm_util.h"
+#include "kselftest_harness.h"
+
+#define MB (1UL << 20)
+
+/* Just the flags we need, copied from the kernel internals. */
+#define FOLL_WRITE	0x01	/* check pte is writable */
+
+/* Page counts exercising single, THP-batch, partial, and full-mapping GUP. */
+static const int nr_pages_list[] = { 1, 512, 123, -1 };
+
+#define GUP_TEST_FILE "/sys/kernel/debug/gup_test"
+#define NR_HUGETLB_PAGES 2
+
+static unsigned long hp_size;
+
+FIXTURE(gup_test)
+{
+	int gup_fd;
+	char *addr;
+	unsigned long size;
+};
+
+FIXTURE_VARIANT(gup_test)
+{
+	bool thp;
+	bool hugetlb;
+	bool write;
+	bool shared;
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_write)
+{
+	.thp = false,
+	.hugetlb = false,
+	.write = true,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_read)
+{
+	.thp = false,
+	.hugetlb = false,
+	.write = false,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_write_thp)
+{
+	.thp = true,
+	.hugetlb = false,
+	.write = true,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_read_thp)
+{
+	.thp = true,
+	.hugetlb = false,
+	.write = false,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_write_hugetlb)
+{
+	.thp = false,
+	.hugetlb = true,
+	.write = true,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, private_read_hugetlb)
+{
+	.thp = false,
+	.hugetlb = true,
+	.write = false,
+	.shared = false,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_write)
+{
+	.thp = false,
+	.hugetlb = false,
+	.write = true,
+	.shared = true,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_read)
+{
+	.thp = false,
+	.hugetlb = false,
+	.write = false,
+	.shared = true,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_write_thp)
+{
+	.thp = true,
+	.hugetlb = false,
+	.write = true,
+	.shared = true,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_read_thp)
+{
+	.thp = true,
+	.hugetlb = false,
+	.write = false,
+	.shared = true,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_write_hugetlb)
+{
+	.thp = false,
+	.hugetlb = true,
+	.write = true,
+	.shared = true,
+};
+
+FIXTURE_VARIANT_ADD(gup_test, shared_read_hugetlb)
+{
+	.thp = false,
+	.hugetlb = true,
+	.write = false,
+	.shared = true,
+};
+
+FIXTURE_SETUP(gup_test)
+{
+	int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS;
+	char *p;
+
+	self->size = 128 * MB;
+
+	if (variant->hugetlb) {
+		if (!hp_size)
+			SKIP(return, "HugeTLB not available\n");
+
+		if (hugetlb_free_default_pages() < NR_HUGETLB_PAGES)
+			SKIP(return, "Not enough huge pages\n");
+
+		self->size = NR_HUGETLB_PAGES * hp_size;
+		mmap_flags |= MAP_HUGETLB;
+	}
+
+	if (variant->shared)
+		mmap_flags = (mmap_flags & ~MAP_PRIVATE) | MAP_SHARED;
+
+	/* gup_fd has to be >= 0. Already checked in main() */
+	self->gup_fd = open(GUP_TEST_FILE, O_RDWR);
+	ASSERT_GE(self->gup_fd, 0);
+
+	self->addr = mmap(NULL, self->size, PROT_READ | PROT_WRITE,
+			  mmap_flags, -1, 0);
+
+	ASSERT_NE(self->addr, MAP_FAILED) {
+		int err = errno;
+
+		close(self->gup_fd);
+		TH_LOG("mmap failed: %s", strerror(err));
+	}
+
+	if (variant->thp)
+		madvise(self->addr, self->size, MADV_HUGEPAGE);
+	else if (!variant->hugetlb)
+		madvise(self->addr, self->size, MADV_NOHUGEPAGE);
+
+	for (p = self->addr; (unsigned long)p < (unsigned long)self->addr
+			+ self->size; p += psize())
+		p[0] = 0;
+}
+
+FIXTURE_TEARDOWN(gup_test)
+{
+	munmap(self->addr, self->size);
+	close(self->gup_fd);
+}
+
+static void run_gup_cmd(struct __test_metadata *_metadata,
+		FIXTURE_DATA(gup_test) *self,
+		const FIXTURE_VARIANT(gup_test) *variant,
+		unsigned long command)
+{
+	int i;
+
+	for (i = 0; i < (int)ARRAY_SIZE(nr_pages_list); i++) {
+		struct gup_test gup = {
+			.addr = (unsigned long)self->addr,
+			.size = self->size,
+			.nr_pages_per_call = nr_pages_list[i] < 0 ?
+				self->size / psize() : nr_pages_list[i],
+			.gup_flags = variant->write ? FOLL_WRITE : 0,
+		};
+
+		TH_LOG("nr_pages_per_call=%u", gup.nr_pages_per_call);
+		ASSERT_EQ(ioctl(self->gup_fd, command, &gup), 0);
+		ASSERT_EQ(gup.size, self->size);
+	}
+}
+
+TEST_F(gup_test, get_user_pages)
+{
+	run_gup_cmd(_metadata, self, variant, GUP_BASIC_TEST);
+}
+
+TEST_F(gup_test, pin_user_pages)
+{
+	run_gup_cmd(_metadata, self, variant, PIN_BASIC_TEST);
+}
+
+TEST_F(gup_test, get_user_pages_fast)
+{
+	run_gup_cmd(_metadata, self, variant, GUP_FAST_BENCHMARK);
+}
+
+TEST_F(gup_test, pin_user_pages_fast)
+{
+	run_gup_cmd(_metadata, self, variant, PIN_FAST_BENCHMARK);
+}
+
+TEST_F(gup_test, pin_user_pages_longterm)
+{
+	run_gup_cmd(_metadata, self, variant, PIN_LONGTERM_BENCHMARK);
+}
+
+int main(int argc, char **argv)
+{
+	const int fd = open(GUP_TEST_FILE, O_RDWR);
+
+	if (fd == -1) {
+		ksft_print_header();
+		if (errno == EACCES)
+			ksft_exit_skip("Please run this test as root\n");
+		if (errno == ENOENT) {
+			DIR *debugfs = opendir("/sys/kernel/debug");
+
+			if (!debugfs)
+				ksft_exit_skip("Mount debugfs at /sys/kernel/debug\n");
+			closedir(debugfs);
+			ksft_exit_skip("Check CONFIG_GUP_TEST in kernel config\n");
+		}
+		ksft_exit_fail_msg("Failed to open %s: %s\n", GUP_TEST_FILE, strerror(errno));
+	}
+	close(fd);
+
+	hp_size = default_huge_page_size();
+	if (hp_size)
+		hugetlb_setup_default(NR_HUGETLB_PAGES);
+
+	return test_harness_run(argc, argv);
+}
diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 4281bb6a859e..0d8c93087d05 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -269,6 +269,7 @@ fi
 
 CATEGORY="mmap" run_test ./map_fixed_noreplace
 
+CATEGORY="gup_test" run_test ./gup
 CATEGORY="gup_test" run_test ./gup_longterm
 
 CATEGORY="userfaultfd" run_test ./uffd-unit-tests