[RFC PATCH v2 46/47] selftests/vm: add hugetlb HGM test to migration selftest

[James Houghton <jthoughton@google.com>]

This is mostly the same as the shared HugeTLB case, but instead of
mapping the page with a regular page fault, we map it with lots of
UFFDIO_CONTINUE operations. We also verify that the contents haven't
changed after the migration, which would be the case if the
post-migration PTEs pointed to the wrong page.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 tools/testing/selftests/vm/migration.c | 139 +++++++++++++++++++++++++
 1 file changed, 139 insertions(+)

diff --git a/tools/testing/selftests/vm/migration.c b/tools/testing/selftests/vm/migration.c
index 21577a84d7e4..89cb5934f139 100644
--- a/tools/testing/selftests/vm/migration.c
+++ b/tools/testing/selftests/vm/migration.c
@@ -14,6 +14,11 @@
 #include <signal.h>
 #include <time.h>
 #include <sys/statfs.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <linux/userfaultfd.h>
+#include <sys/syscall.h>
+#include <fcntl.h>
 
 #define TWOMEG (2<<20)
 #define RUNTIME (60)
@@ -265,4 +270,138 @@ TEST_F_TIMEOUT(migration, shared_hugetlb, 2*RUNTIME)
 	close(fd);
 }
 
+#ifdef __NR_userfaultfd
+static int map_at_high_granularity(char *mem, size_t length)
+{
+	int i;
+	int ret;
+	int uffd = syscall(__NR_userfaultfd, 0);
+	struct uffdio_api api;
+	struct uffdio_register reg;
+	int pagesize = getpagesize();
+
+	if (uffd < 0) {
+		perror("couldn't create uffd");
+		return uffd;
+	}
+
+	api.api = UFFD_API;
+	api.features = UFFD_FEATURE_MISSING_HUGETLBFS
+		| UFFD_FEATURE_MINOR_HUGETLBFS
+		| UFFD_FEATURE_MINOR_HUGETLBFS_HGM;
+
+	ret = ioctl(uffd, UFFDIO_API, &api);
+	if (ret || api.api != UFFD_API) {
+		perror("UFFDIO_API failed");
+		goto out;
+	}
+
+	reg.range.start = (unsigned long)mem;
+	reg.range.len = length;
+
+	reg.mode = UFFDIO_REGISTER_MODE_MISSING | UFFDIO_REGISTER_MODE_MINOR;
+
+	ret = ioctl(uffd, UFFDIO_REGISTER, &reg);
+	if (ret) {
+		perror("UFFDIO_REGISTER failed");
+		goto out;
+	}
+
+	/* UFFDIO_CONTINUE each 4K segment of the 2M page. */
+	for (i = 0; i < length/pagesize; ++i) {
+		struct uffdio_continue cont;
+
+		cont.range.start = (unsigned long long)mem + i * pagesize;
+		cont.range.len = pagesize;
+		cont.mode = 0;
+		ret = ioctl(uffd, UFFDIO_CONTINUE, &cont);
+		if (ret) {
+			fprintf(stderr, "UFFDIO_CONTINUE failed "
+					"for %llx -> %llx: %d\n",
+					cont.range.start,
+					cont.range.start + cont.range.len,
+					errno);
+			goto out;
+		}
+	}
+	ret = 0;
+out:
+	close(uffd);
+	return ret;
+}
+#else
+static int map_at_high_granularity(char *mem, size_t length)
+{
+	fprintf(stderr, "Userfaultfd missing\n");
+	return -1;
+}
+#endif /* __NR_userfaultfd */
+
+/*
+ * Tests the high-granularity hugetlb migration entry paths.
+ */
+TEST_F_TIMEOUT(migration, shared_hugetlb_hgm, 2*RUNTIME)
+{
+	uint64_t *ptr;
+	int i;
+	int fd;
+	unsigned long sz;
+	struct statfs filestat;
+
+	if (self->nthreads < 2 || self->n1 < 0 || self->n2 < 0)
+		SKIP(return, "Not enough threads or NUMA nodes available");
+
+	fd = memfd_create("tmp_hugetlb", MFD_HUGETLB);
+	if (fd < 0)
+		SKIP(return, "Couldn't create hugetlb memfd");
+
+	if (fstatfs(fd, &filestat) < 0)
+		SKIP(return, "Couldn't fstatfs hugetlb file");
+
+	sz = filestat.f_bsize;
+
+	if (ftruncate(fd, sz))
+		SKIP(return, "Couldn't allocate hugetlb pages");
+
+	if (fallocate(fd, 0, 0, sz) < 0) {
+		perror("fallocate failed");
+		SKIP(return, "fallocate failed");
+	}
+
+	ptr = mmap(NULL, sz, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (ptr == MAP_FAILED)
+		SKIP(return, "Could not allocate hugetlb pages");
+
+	/*
+	 * We have to map_at_high_granularity before we memset, otherwise
+	 * memset will map everything at the hugepage size.
+	 */
+	if (map_at_high_granularity((char *)ptr, sz) < 0)
+		SKIP(return, "Could not map HugeTLB range at high granularity");
+
+	/* Populate the page we're migrating. */
+	for (i = 0; i < sz/sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	for (i = 0; i < self->nthreads - 1; i++)
+		if (pthread_create(&self->threads[i], NULL, access_mem, ptr))
+			perror("Couldn't create thread");
+
+	ASSERT_EQ(migrate(ptr, self->n1, self->n2, 10), 0);
+	for (i = 0; i < self->nthreads - 1; i++) {
+		ASSERT_EQ(pthread_cancel(self->threads[i]), 0);
+		pthread_join(self->threads[i], NULL);
+	}
+
+	/* Check that the contents didnt' change. */
+	for (i = 0; i < sz/sizeof(*ptr); ++i) {
+		ASSERT_EQ(ptr[i], i);
+		if (ptr[i] != i)
+			break;
+	}
+
+	ftruncate(fd, 0);
+	close(fd);
+}
+
 TEST_HARNESS_MAIN
-- 
2.38.0.135.g90850a2211-goog