[PATCH 2/5] KVM: selftests: add shmem backing source type

[Axel Rasmussen <axelrasmussen@google.com>]

This lets us run the demand paging test on top of a shmem-backed area.
In follow-up commits, we'll 1) leverage this new capability to create an
alias mapping, and then 2) use the alias mapping to exercise UFFD minor
faults.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
 .../testing/selftests/kvm/include/test_util.h |  1 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 24 ++++++++---
 tools/testing/selftests/kvm/lib/test_util.c   | 40 +++++++++++--------
 3 files changed, 44 insertions(+), 21 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index fade3130eb01..7377f00469ef 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -84,6 +84,7 @@ enum vm_mem_backing_src_type {
 	VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB,
 	VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB,
 	VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB,
+	VM_MEM_SRC_SHMEM,
 	NUM_SRC_TYPES,
 };
 
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index fc83f6c5902d..6fbe124e0e16 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -663,8 +663,8 @@ int kvm_memcmp_hva_gva(void *hva, struct kvm_vm *vm, vm_vaddr_t gva, size_t len)
  *
  * Input Args:
  *   vm - Virtual Machine
- *   backing_src - Storage source for this region.
- *                 NULL to use anonymous memory.
+ *   src_type - Storage source for this region.
+ *              NULL to use anonymous memory.
  *   guest_paddr - Starting guest physical address
  *   slot - KVM region slot
  *   npages - Number of physical pages
@@ -755,11 +755,25 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 	if (alignment > 1)
 		region->mmap_size += alignment;
 
+	region->fd = -1;
+	if (src_type == VM_MEM_SRC_SHMEM) {
+		region->fd = memfd_create("kvm_selftest", MFD_CLOEXEC);
+		TEST_ASSERT(region->fd != -1,
+			    "memfd_create failed, errno: %i", errno);
+
+		ret = ftruncate(region->fd, region->mmap_size);
+		TEST_ASSERT(ret == 0, "ftruncate failed, errno: %i", errno);
+
+		ret = fallocate(region->fd,
+				FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
+				region->mmap_size);
+		TEST_ASSERT(ret == 0, "fallocate failed, errno: %i", errno);
+	}
+
 	region->mmap_start = mmap(NULL, region->mmap_size,
 				  PROT_READ | PROT_WRITE,
-				  MAP_PRIVATE | MAP_ANONYMOUS
-				  | vm_mem_backing_src_alias(src_type)->flag,
-				  -1, 0);
+				  vm_mem_backing_src_alias(src_type)->flag,
+				  region->fd, 0);
 	TEST_ASSERT(region->mmap_start != MAP_FAILED,
 		    "test_malloc failed, mmap_start: %p errno: %i",
 		    region->mmap_start, errno);
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 63d2bc7d757b..c7a265da5090 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -168,70 +168,77 @@ size_t get_def_hugetlb_pagesz(void)
 
 const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
 {
+	static const int anon_flags = MAP_PRIVATE | MAP_ANONYMOUS;
+	static const int anon_huge_flags = anon_flags | MAP_HUGETLB;
+
 	static const struct vm_mem_backing_src_alias aliases[] = {
 		[VM_MEM_SRC_ANONYMOUS] = {
 			.name = "anonymous",
-			.flag = 0,
+			.flag = anon_flags,
 		},
 		[VM_MEM_SRC_ANONYMOUS_THP] = {
 			.name = "anonymous_thp",
-			.flag = 0,
+			.flag = anon_flags,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB] = {
 			.name = "anonymous_hugetlb",
-			.flag = MAP_HUGETLB,
+			.flag = anon_huge_flags,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_16KB] = {
 			.name = "anonymous_hugetlb_16kb",
-			.flag = MAP_HUGETLB | MAP_HUGE_16KB,
+			.flag = anon_huge_flags | MAP_HUGE_16KB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_64KB] = {
 			.name = "anonymous_hugetlb_64kb",
-			.flag = MAP_HUGETLB | MAP_HUGE_64KB,
+			.flag = anon_huge_flags | MAP_HUGE_64KB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_512KB] = {
 			.name = "anonymous_hugetlb_512kb",
-			.flag = MAP_HUGETLB | MAP_HUGE_512KB,
+			.flag = anon_huge_flags | MAP_HUGE_512KB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_1MB] = {
 			.name = "anonymous_hugetlb_1mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_1MB,
+			.flag = anon_huge_flags | MAP_HUGE_1MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_2MB] = {
 			.name = "anonymous_hugetlb_2mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_2MB,
+			.flag = anon_huge_flags | MAP_HUGE_2MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_8MB] = {
 			.name = "anonymous_hugetlb_8mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_8MB,
+			.flag = anon_huge_flags | MAP_HUGE_8MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_16MB] = {
 			.name = "anonymous_hugetlb_16mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_16MB,
+			.flag = anon_huge_flags | MAP_HUGE_16MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_32MB] = {
 			.name = "anonymous_hugetlb_32mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_32MB,
+			.flag = anon_huge_flags | MAP_HUGE_32MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_256MB] = {
 			.name = "anonymous_hugetlb_256mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_256MB,
+			.flag = anon_huge_flags | MAP_HUGE_256MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_512MB] = {
 			.name = "anonymous_hugetlb_512mb",
-			.flag = MAP_HUGETLB | MAP_HUGE_512MB,
+			.flag = anon_huge_flags | MAP_HUGE_512MB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB] = {
 			.name = "anonymous_hugetlb_1gb",
-			.flag = MAP_HUGETLB | MAP_HUGE_1GB,
+			.flag = anon_huge_flags | MAP_HUGE_1GB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB] = {
 			.name = "anonymous_hugetlb_2gb",
-			.flag = MAP_HUGETLB | MAP_HUGE_2GB,
+			.flag = anon_huge_flags | MAP_HUGE_2GB,
 		},
 		[VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB] = {
 			.name = "anonymous_hugetlb_16gb",
-			.flag = MAP_HUGETLB | MAP_HUGE_16GB,
+			.flag = anon_huge_flags | MAP_HUGE_16GB,
+		},
+		[VM_MEM_SRC_SHMEM] = {
+			.name = "shmem",
+			.flag = MAP_SHARED,
 		},
 	};
 	_Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
@@ -250,6 +257,7 @@ size_t get_backing_src_pagesz(uint32_t i)
 
 	switch (i) {
 	case VM_MEM_SRC_ANONYMOUS:
+	case VM_MEM_SRC_SHMEM:
 		return getpagesize();
 	case VM_MEM_SRC_ANONYMOUS_THP:
 		return get_trans_hugepagesz();
-- 
2.31.1.607.g51e8a6a459-goog