[PATCH v4 07/12] KVM: selftests: set KVM_MEM_GUEST_MEMFD in vm_mem_add() if guest_memfd != -1

[Patrick Roy]

Have vm_mem_add() always set KVM_MEM_GUEST_MEMFD in the memslot flags if
a guest_memfd is passed in as an argument. This eliminates the
possibility where a guest_memfd instance is passed to vm_mem_add(), but
it ends up being ignored because the flags argument does not specify
KVM_MEM_GUEST_MEMFD at the same time.

This makes it easy to support more scenarios in which no vm_mem_add() is
not passed a guest_memfd instance, but is expected to allocate one.
Currently, this only happens if guest_memfd == -1 but flags &
KVM_MEM_GUEST_MEMFD != 0, but later vm_mem_add() will gain support for
loading the test code itself into guest_memfd (via KVM_GMEM_SHARED_MEM)
if requested via a special vm_mem_backing_src_type, at which point
having to make sure the src_type and flags are in-sync becomes
cumbersome.

Signed-off-by: Patrick Roy <roy...@amazon.co.uk>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 26 +++++++++++++---------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c 
b/tools/testing/selftests/kvm/lib/kvm_util.c
index 33fefeb3ca44..ebdf38e2983b 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1017,22 +1017,26 @@ void vm_mem_add(struct kvm_vm *vm, enum 
vm_mem_backing_src_type src_type,
 
        region->backing_src_type = src_type;
 
-       if (flags & KVM_MEM_GUEST_MEMFD) {
-               if (guest_memfd < 0) {
+       if (guest_memfd < 0) {
+               if (flags & KVM_MEM_GUEST_MEMFD) {
                        uint32_t guest_memfd_flags = 0;
                        TEST_ASSERT(!guest_memfd_offset,
                                    "Offset must be zero when creating new 
guest_memfd");
                        guest_memfd = vm_create_guest_memfd(vm, mem_size, 
guest_memfd_flags);
-               } else {
-                       /*
-                        * Install a unique fd for each memslot so that the fd
-                        * can be closed when the region is deleted without
-                        * needing to track if the fd is owned by the framework
-                        * or by the caller.
-                        */
-                       guest_memfd = dup(guest_memfd);
-                       TEST_ASSERT(guest_memfd >= 0, 
__KVM_SYSCALL_ERROR("dup()", guest_memfd));
                }
+       } else {
+               /*
+                * Install a unique fd for each memslot so that the fd
+                * can be closed when the region is deleted without
+                * needing to track if the fd is owned by the framework
+                * or by the caller.
+                */
+               guest_memfd = dup(guest_memfd);
+               TEST_ASSERT(guest_memfd >= 0, __KVM_SYSCALL_ERROR("dup()", 
guest_memfd));
+       }
+
+       if (guest_memfd > 0) {
+               flags |= KVM_MEM_GUEST_MEMFD;
 
                region->region.guest_memfd = guest_memfd;
                region->region.guest_memfd_offset = guest_memfd_offset;
-- 
2.48.1