[PATCH v15 13/23] KVM: selftests: Support guest_memfd in-place conversion

[Lisa Wang <wyihan@google.com>]

With guest_memfd in-place conversion, the memory region can be set as
shared, eliminating the need for dual-backed memory.

By setting the region to shared initially, the KVM selftest framework
can populate the mmap()-ed guest_memfd memory just like any standard
memory provider.

For CoCo VMs, pages that need to be private are explicitly set to
private before executing the VM.

Signed-off-by: Lisa Wang <wyihan@google.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c         | 20 ++++++++++++++------
 tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c |  6 +++++-
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 7625908caf21..f474664b5d92 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -494,8 +494,10 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus,
 	u64 nr_pages = vm_nr_pages_required(shape.mode, nr_runnable_vcpus,
 						 nr_extra_pages);
 	struct userspace_mem_region *slot0;
+	u64 gmem_flags = 0;
 	struct kvm_vm *vm;
-	int i, flags;
+	int flags = 0;
+	int i;
 
 	kvm_set_files_rlimit(nr_runnable_vcpus);
 
@@ -505,14 +507,20 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus,
 	vm = ____vm_create(shape);
 
 	/*
-	 * Force GUEST_MEMFD for the primary memory region if necessary, e.g.
-	 * for CoCo VMs that require GUEST_MEMFD backed private memory.
+	 * Force GUEST_MEMFD for the primary memory region if necessary, and
+	 * initialize it as shared if in-place conversion is supported, so the
+	 * selftest framework can populate it exactly like other memory
+	 * providers.
 	 */
-	flags = 0;
-	if (is_guest_memfd_required(shape))
+	if (is_guest_memfd_required(shape)) {
 		flags |= KVM_MEM_GUEST_MEMFD;
+		if (kvm_has_gmem_attributes)
+			gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED |
+				      GUEST_MEMFD_FLAG_MMAP;
+	}
 
-	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, nr_pages, flags);
+	vm_mem_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, nr_pages, flags,
+		   -1, 0, gmem_flags);
 	for (i = 0; i < NR_MEM_REGIONS; i++)
 		vm->memslots[i] = 0;
 
diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
index e348507a6be8..40ee9b1951c2 100644
--- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
+++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
@@ -23,6 +23,8 @@ void tdx_vm_setup_boot_code_region(struct kvm_vm *vm)
 	gpa_t gpa;
 	u8 *hva;
 
+	if (kvm_has_gmem_attributes)
+		gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED | GUEST_MEMFD_FLAG_MMAP;
 	vm_mem_add(vm, VM_MEM_SRC_SHMEM, alloc_gpa, TD_BOOT_CODE_SLOT,
 		   nr_pages, KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);
 
@@ -44,9 +46,11 @@ void tdx_vm_setup_boot_parameters_region(struct kvm_vm *vm, u32 nr_runnable_vcpu
 	size_t boot_params_size = sizeof(struct td_boot_parameters) +
 		nr_runnable_vcpus * sizeof(struct td_per_vcpu_parameters);
 	int npages = DIV_ROUND_UP(boot_params_size, PAGE_SIZE);
-	const u64 gmem_flags = 0;
+	u64 gmem_flags = 0;
 	gpa_t gpa;
 
+	if (kvm_has_gmem_attributes)
+		gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED | GUEST_MEMFD_FLAG_MMAP;
 	vm_mem_add(vm, VM_MEM_SRC_SHMEM, TD_BOOT_PARAMETERS_GPA,
 		   TD_BOOT_PARAMETERS_SLOT, npages,
 		   KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);

-- 
2.56.0.rc1.315.gc6ed9934b7-goog