[RFC PATCH 2/4] KVM: selftests: Align memory region addresses to 1M on s390x

[Thomas Huth]

On s390x, there is a constraint that memory regions have to be aligned
to 1M (or running the VM will fail). Introduce a new "alignment" variable
in the vm_userspace_mem_region_add() function which now can be used for
both, huge page and s390x alignment requirements.

Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 21 +++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 8d63ccb93e10..64a0da6efe3d 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -559,6 +559,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 	unsigned long pmem_size = 0;
 	struct userspace_mem_region *region;
 	size_t huge_page_size = KVM_UTIL_PGS_PER_HUGEPG * vm->page_size;
+	size_t alignment;
 
 	TEST_ASSERT((guest_paddr % vm->page_size) == 0, "Guest physical "
 		"address not on a page boundary.\n"
@@ -608,9 +609,20 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 	TEST_ASSERT(region != NULL, "Insufficient Memory");
 	region->mmap_size = npages * vm->page_size;
 
-	/* Enough memory to align up to a huge page. */
+#ifdef __s390x__
+	/* On s390x, the host address must be aligned to 1M (due to PGSTEs) */
+	alignment = 0x100000;
+#else
+	alignment = 1;
+#endif
+
 	if (src_type == VM_MEM_SRC_ANONYMOUS_THP)
-		region->mmap_size += huge_page_size;
+		alignment = huge_page_size;
+
+	/* Add enough memory to align up if necessary */
+	if (alignment > 1)
+		region->mmap_size += alignment;
+
 	region->mmap_start = mmap(NULL, region->mmap_size,
 				  PROT_READ | PROT_WRITE,
 				  MAP_PRIVATE | MAP_ANONYMOUS
@@ -620,9 +632,8 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 		    "test_malloc failed, mmap_start: %p errno: %i",
 		    region->mmap_start, errno);
 
-	/* Align THP allocation up to start of a huge page. */
-	region->host_mem = align(region->mmap_start,
-				 src_type == VM_MEM_SRC_ANONYMOUS_THP ?  huge_page_size : 1);
+	/* Align host address */
+	region->host_mem = align(region->mmap_start, alignment);
 
 	/* As needed perform madvise */
 	if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
-- 
2.21.0