[PATCH V4 2/2] selftests: vm: Add test for Soft-Dirty PTE bit

Muhammad Usama Anjum
2022-03-15T08:51:06Z

From: Gabriel Krisman Bertazi <krisman@collabora.com>

This introduces three tests:
1) Sanity check soft dirty basic semantics: allocate area, clean, dirty,
check if the SD bit is flipped.
2) Check VMA reuse: validate the VM_SOFTDIRTY usage
3) Check soft-dirty on huge pages

This was motivated by Will Deacon's fix commit 912efa17e512 ("mm: proc:
Invalidate TLB after clearing soft-dirty page state"). I was tracking the
same issue that he fixed, and this test would have caught it.

CC: Will Deacon <will@kernel.org>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
---
V3 of this patch is in Andrew's tree. Please drop that.

Changes in V4:
Cosmetic changes
Removed global variables
Replaced ksft_print_msg with ksft_exit_fail_msg to exit the program at
once
Some other minor changes
Correct the authorship of the patch

Tests of soft dirty bit in this patch and in madv_populate.c are
non-overlapping. madv_populate.c has only one soft-dirty bit test in the
context of different advise (MADV_POPULATE_READ and
MADV_POPULATE_WRITE). This new test adds more tests.

Tab width of 8 has been used to align the macros. This alignment may look
odd in shell or email. But it looks alright in editors.

Test output:
TAP version 13
1..5
ok 1 Test test_simple
ok 2 Test test_vma_reuse reused memory location
ok 3 Test test_vma_reuse dirty bit of previous page
ok 4 Test test_hugepage huge page allocation
ok 5 Test test_hugepage huge page dirty bit
# Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0

Or

TAP version 13
1..5
ok 1 Test test_simple
ok 2 Test test_vma_reuse reused memory location
ok 3 Test test_vma_reuse dirty bit of previous page
ok 4 # SKIP Test test_hugepage huge page allocation
ok 5 # SKIP Test test_hugepage huge page dirty bit
# Totals: pass:3 fail:0 xfail:0 xpass:0 skip:2 error:0

Changes in V3:
Move test to selftests/vm
Use kselftest macros
Minor updates to make code more maintainable
Add configurations in config file

V2 of this patch:
https://lore.kernel.org/lkml/20210603151518.2437813-1-krisman@collabora.com/
---
tools/testing/selftests/vm/.gitignore | 1 +
tools/testing/selftests/vm/Makefile | 2 +
tools/testing/selftests/vm/config | 2 +
tools/testing/selftests/vm/soft-dirty.c | 146 ++++++++++++++++++++++++
4 files changed, 151 insertions(+)
create mode 100644 tools/testing/selftests/vm/soft-dirty.c

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index d7507f3c7c76a..3cb4fa771ec2a 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -29,5 +29,6 @@ write_to_hugetlbfs
hmm-tests
memfd_secret
local_config.*
+soft-dirty
split_huge_page_test
ksm_tests
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 4e68edb26d6b6..f25eb30b5f0cb 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -47,6 +47,7 @@ TEST_GEN_FILES += on-fault-limit
TEST_GEN_FILES += thuge-gen
TEST_GEN_FILES += transhuge-stress
TEST_GEN_FILES += userfaultfd
+TEST_GEN_PROGS += soft-dirty
TEST_GEN_PROGS += split_huge_page_test
TEST_GEN_FILES += ksm_tests

@@ -92,6 +93,7 @@ KSFT_KHDR_INSTALL := 1
include ../lib.mk

$(OUTPUT)/madv_populate: vm_util.c
+$(OUTPUT)/soft-dirty: vm_util.c
$(OUTPUT)/split_huge_page_test: vm_util.c

ifeq ($(MACHINE),x86_64)
diff --git a/tools/testing/selftests/vm/config b/tools/testing/selftests/vm/config
index 60e82da0de850..be087c4bc3961 100644
--- a/tools/testing/selftests/vm/config
+++ b/tools/testing/selftests/vm/config
@@ -4,3 +4,5 @@ CONFIG_TEST_VMALLOC=m
CONFIG_DEVICE_PRIVATE=y
CONFIG_TEST_HMM=m
CONFIG_GUP_TEST=y
+CONFIG_TRANSPARENT_HUGEPAGE=y
+CONFIG_MEM_SOFT_DIRTY=y
diff --git a/tools/testing/selftests/vm/soft-dirty.c b/tools/testing/selftests/vm/soft-dirty.c
new file mode 100644
index 0000000000000..2d50ed3472206
--- /dev/null
+++ b/tools/testing/selftests/vm/soft-dirty.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <malloc.h>
+#include <sys/mman.h>
+#include "../kselftest.h"
+#include "vm_util.h"
+
+#define PAGEMAP "/proc/self/pagemap"
+#define CLEAR_REFS "/proc/self/clear_refs"
+#define MAX_LINE_LENGTH 512
+#define TEST_ITERATIONS 10000
+
+static void test_simple(int pagemap_fd, int pagesize)
+{
+ int i;
+ char *map;
+
+ map = aligned_alloc(pagesize, pagesize);
+ if (!map)
+ ksft_exit_fail_msg("mmap failed\n");
+
+ clear_softdirty();
+
+ for (i = 0 ; i < TEST_ITERATIONS; i++) {
+ if (pagemap_is_softdirty(pagemap_fd, map) == 1) {
+ ksft_print_msg("dirty bit was 1, but should be 0 (i=%d)\n", i);
+ break;
+ }
+
+ clear_softdirty();
+ map[0]++;
+
+ if (pagemap_is_softdirty(pagemap_fd, map) == 0) {
+ ksft_print_msg("dirty bit was 0, but should be 1 (i=%d)\n", i);
+ break;
+ }
+
+ clear_softdirty();
+ }
+ free(map);
+
+ ksft_test_result(i == TEST_ITERATIONS, "Test %s\n", __func__);
+}
+
+static void test_vma_reuse(int pagemap_fd, int pagesize)
+{
+ char *map, *map2;
+
+ map = mmap(NULL, pagesize, (PROT_READ | PROT_WRITE), (MAP_PRIVATE | MAP_ANON), -1, 0);
+ if (map == MAP_FAILED)
+ ksft_exit_fail_msg("mmap failed");
+
+ clear_softdirty();
+
+ /* Write to the page before unmapping and map the same size region again to check
+ * if same memory region is gotten next time and if dirty bit is preserved across
+ * this type of allocations.
+ */
+ map[0]++;
+
+ munmap(map, pagesize);
+
+ map2 = mmap(NULL, pagesize, (PROT_READ | PROT_WRITE), (MAP_PRIVATE | MAP_ANON), -1, 0);
+ if (map2 == MAP_FAILED)
+ ksft_exit_fail_msg("mmap failed");
+
+ ksft_test_result(map == map2, "Test %s reused memory location\n", __func__);
+
+ ksft_test_result(pagemap_is_softdirty(pagemap_fd, map) != 0,
+ "Test %s dirty bit of previous page\n", __func__);
+
+ munmap(map2, pagesize);
+}
+
+static void test_hugepage(int pagemap_fd, int pagesize)
+{
+ char *map;
+ int i, ret;
+ size_t hpage_len = read_pmd_pagesize();
+
+ map = memalign(hpage_len, hpage_len);
+ if (!map)
+ ksft_exit_fail_msg("memalign failed\n");
+
+ ret = madvise(map, hpage_len, MADV_HUGEPAGE);
+ if (ret)
+ ksft_exit_fail_msg("madvise failed %d\n", ret);
+
+ for (i = 0; i < hpage_len; i++)
+ map[i] = (char)i;
+
+ if (check_huge(map)) {
+ ksft_test_result_pass("Test %s huge page allocation\n", __func__);
+
+ clear_softdirty();
+ for (i = 0 ; i < TEST_ITERATIONS ; i++) {
+ if (pagemap_is_softdirty(pagemap_fd, map) == 1) {
+ ksft_print_msg("dirty bit was 1, but should be 0 (i=%d)\n", i);
+ break;
+ }
+
+ clear_softdirty();
+ map[0]++;
+
+ if (pagemap_is_softdirty(pagemap_fd, map) == 0) {
+ ksft_print_msg("dirty bit was 0, but should be 1 (i=%d)\n", i);
+ break;
+ }
+ clear_softdirty();
+ }
+
+ ksft_test_result(i == TEST_ITERATIONS, "Test %s huge page dirty bit\n", __func__);
+ } else {
+ // hugepage allocation failed. skip these tests
+ ksft_test_result_skip("Test %s huge page allocation\n", __func__);
+ ksft_test_result_skip("Test %s huge page dirty bit\n", __func__);
+ }
+ free(map);
+}
+
+int main(int argc, char **argv)
+{
+ int pagemap_fd;
+ int pagesize;
+
+ ksft_print_header();
+ ksft_set_plan(5);
+
+ pagemap_fd = open(PAGEMAP, O_RDONLY);
+ if (pagemap_fd < 0)
+ ksft_exit_fail_msg("Failed to open %s\n", PAGEMAP);
+
+ pagesize = getpagesize();
+
+ test_simple(pagemap_fd, pagesize);
+ test_vma_reuse(pagemap_fd, pagesize);
+ test_hugepage(pagemap_fd, pagesize);
+
+ close(pagemap_fd);
+
+ return ksft_exit_pass();
+}
--
2.30.2