[PATCH v12 44/45] KVM: selftests: Update private_mem_conversions_test for in-place conversions

[Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>]

From: Ackerley Tng <ackerleytng@google.com>

Update private_mem_conversions_test for in-place conversions. In-place
conversions support is detected in selftests with kvm_has_gmem_attributes.

With in-place conversions, specifying userspace_addr from some other memory
provider that is not the guest_memfd associated with the memslot is a user
error, since KVM will only use both shared and private memory from the
guest_memfd.

Hence, when kvm_has_gmem_attributes, only test in-place conversions with
single backing, where guest_memfd provides both shared and private memory.

For single backing, guest_memfd must be created with
GUEST_MEMFD_FLAG_MMAP. Initialize the guest_memfd as shared to align with
how memory would default to shared when shared/private state was tracked at
the VM level (the test expects this, it was written for
non-in-place-conversions).

When handling a hypercall to set attributes, use
vm_mem_set_memory_attributes() to send the ioctl to the guest_memfd instead
of the VM.

When testing in-place conversions (single-backing), don't allow the user to
configure src_type, since src_type will be ignored. Don't use src_type to
determine alignment for rounding up per-cpu test memory size, since
guest_memfd's backing page size is always the system PAGE_SIZE.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../kvm/x86/private_mem_conversions_test.c         | 57 +++++++++++++++++-----
 1 file changed, 44 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index cf50e9a332c5b..33b610383693b 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -306,9 +306,12 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
 	if (do_fallocate)
 		vm_guest_mem_fallocate(vm, gpa, size, map_shared);
 
-	if (set_attributes)
-		vm_set_memory_attributes(vm, gpa, size,
-					 map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
+	if (set_attributes) {
+		u64 attrs = map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
+		vm_mem_set_memory_attributes(vm, gpa, size, attrs);
+	}
+
 	run->hypercall.ret = 0;
 }
 
@@ -352,8 +355,21 @@ static void *__test_mem_conversions(void *__vcpu)
 				size_t nr_bytes = min_t(size_t, vm->page_size, size - i);
 				u8 *hva = addr_gpa2hva(vm, gpa + i);
 
-				/* In all cases, the host should observe the shared data. */
-				memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+				if (kvm_has_gmem_attributes &&
+				    uc.args[0] == SYNC_PRIVATE) {
+					TEST_EXPECT_SIGBUS(READ_ONCE(*hva));
+				} else {
+					/*
+					 * If not testing in-place conversion
+					 * (dual backing), the host should
+					 * always observe shared data, since the
+					 * shared memory is a separate page.
+					 *
+					 * For SYNC_SHARED, test that the host
+					 * can see shared memory.
+					 */
+					memcmp_h(hva, gpa + i, uc.args[3], nr_bytes);
+				}
 
 				/* For shared, write the new pattern to guest memory. */
 				if (uc.args[0] == SYNC_SHARED)
@@ -369,20 +385,29 @@ static void *__test_mem_conversions(void *__vcpu)
 	}
 }
 
+/* Align each vCPU's chunk of memory naturally to the size of the backing store. */
+static size_t compute_per_cpu_size(enum vm_mem_backing_src_type src_type)
+{
+	size_t alignment;
+
+	if (kvm_has_gmem_attributes)
+		alignment = getpagesize();
+	else
+		alignment = get_backing_src_pagesz(src_type);
+
+	return align_up(PER_CPU_DATA_SIZE, max_t(size_t, SZ_2M, alignment));
+}
+
 static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_vcpus,
 				 u32 nr_memslots)
 {
-	/*
-	 * Allocate enough memory so that each vCPU's chunk of memory can be
-	 * naturally aligned with respect to the size of the backing store.
-	 */
-	const size_t alignment = max_t(size_t, SZ_2M, get_backing_src_pagesz(src_type));
-	const size_t per_cpu_size = align_up(PER_CPU_DATA_SIZE, alignment);
+	const size_t per_cpu_size = compute_per_cpu_size(src_type);
 	const size_t memfd_size = per_cpu_size * nr_vcpus;
 	const size_t slot_size = memfd_size / nr_memslots;
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 	pthread_t threads[KVM_MAX_VCPUS];
 	struct kvm_vm *vm;
+	u64 gmem_flags;
 	int memfd, i;
 
 	const struct vm_shape shape = {
@@ -397,12 +422,16 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, u32 nr_v
 
 	vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 << KVM_HC_MAP_GPA_RANGE));
 
-	memfd = vm_create_guest_memfd(vm, memfd_size, 0);
+	gmem_flags = 0;
+	if (kvm_has_gmem_attributes)
+		gmem_flags = GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_INIT_SHARED;
+
+	memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags);
 
 	for (i = 0; i < nr_memslots; i++)
 		vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
 			   BASE_DATA_SLOT + i, slot_size / vm->page_size,
-			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0);
+			   KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, gmem_flags);
 
 	for (i = 0; i < nr_vcpus; i++) {
 		gpa_t gpa =  BASE_DATA_GPA + i * per_cpu_size;
@@ -462,6 +491,8 @@ int main(int argc, char *argv[])
 	while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) {
 		switch (opt) {
 		case 's':
+			TEST_ASSERT(!kvm_has_gmem_attributes,
+				    "src_type is only configurable when testing without in-place conversion");
 			src_type = parse_backing_src_type(optarg);
 			break;
 		case 'n':

-- 
2.55.0.897.gb25b4bd76c-goog