[PATCH 5/5] KVM: selftests: add shared hugetlbfs backing source type

[Axel Rasmussen <axelrasmussen@xxxxxxxxxx>]

This lets us run the demand paging test on top of a shared
hugetlbfs-backed area. The "shared" is key, as this allows us to
exercise userfaultfd minor faults on hugetlbfs.

Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/demand_paging_test.c |  6 ++++--
 tools/testing/selftests/kvm/include/test_util.h  | 10 ++++++++++
 tools/testing/selftests/kvm/lib/kvm_util.c       |  9 +++++++--
 tools/testing/selftests/kvm/lib/test_util.c      |  6 ++++++
 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index ff29aaea3120..32942c9e0376 100644
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -502,8 +502,10 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	TEST_ASSERT(p.uffd_mode != UFFDIO_REGISTER_MODE_MINOR || p.src_type == VM_MEM_SRC_SHMEM,
-		    "userfaultfd MINOR mode requires shared memory; pick a different -t");
+	if (p.uffd_mode == UFFDIO_REGISTER_MODE_MINOR &&
+	    !backing_src_is_shared(p.src_type)) {
+		TEST_FAIL("userfaultfd MINOR mode requires shared memory; pick a different -t");
+	}
 
 	for_each_guest_mode(run_test, &p);
 
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index 7377f00469ef..852d6d2cc285 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -85,9 +85,19 @@ enum vm_mem_backing_src_type {
 	VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB,
 	VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB,
 	VM_MEM_SRC_SHMEM,
+	VM_MEM_SRC_SHARED_HUGETLB,
 	NUM_SRC_TYPES,
 };
 
+/*
+ * Whether or not the given source type is shared memory (as opposed to
+ * anonymous).
+ */
+static inline bool backing_src_is_shared(enum vm_mem_backing_src_type t)
+{
+	return t == VM_MEM_SRC_SHMEM || t == VM_MEM_SRC_SHARED_HUGETLB;
+}
+
 struct vm_mem_backing_src_alias {
 	const char *name;
 	uint32_t flag;
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 838d58633f7e..fed02153c919 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -756,8 +756,13 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 		region->mmap_size += alignment;
 
 	region->fd = -1;
-	if (src_type == VM_MEM_SRC_SHMEM) {
-		region->fd = memfd_create("kvm_selftest", MFD_CLOEXEC);
+	if (backing_src_is_shared(src_type)) {
+		int memfd_flags = MFD_CLOEXEC;
+
+		if (src_type == VM_MEM_SRC_SHARED_HUGETLB)
+			memfd_flags |= MFD_HUGETLB;
+
+		region->fd = memfd_create("kvm_selftest", memfd_flags);
 		TEST_ASSERT(region->fd != -1,
 			    "memfd_create failed, errno: %i", errno);
 
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index c7a265da5090..65fb8b43782c 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -240,6 +240,11 @@ const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
 			.name = "shmem",
 			.flag = MAP_SHARED,
 		},
+		[VM_MEM_SRC_SHARED_HUGETLB] = {
+			.name = "shared_hugetlb",
+			/* No MAP_HUGETLB, we use MFD_HUGETLB instead. */
+			.flag = MAP_SHARED,
+		},
 	};
 	_Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
 		       "Missing new backing src types?");
@@ -262,6 +267,7 @@ size_t get_backing_src_pagesz(uint32_t i)
 	case VM_MEM_SRC_ANONYMOUS_THP:
 		return get_trans_hugepagesz();
 	case VM_MEM_SRC_ANONYMOUS_HUGETLB:
+	case VM_MEM_SRC_SHARED_HUGETLB:
 		return get_def_hugetlb_pagesz();
 	default:
 		return MAP_HUGE_PAGE_SIZE(flag);
-- 
2.31.1.607.g51e8a6a459-goog