[PATCH v4 06/13] KVM: selftests: Add vm_mem_region_get_src_fd library function

[Ricardo Koller <ricarkol@google.com>]

Add a library function to get the backing source FD of a memslot.

Reviewed-by: Oliver Upton <oupton@google.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 .../selftests/kvm/include/kvm_util_base.h     |  1 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 54ede9fc923c..72c8881fe8fb 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -322,6 +322,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 void vm_mem_region_set_flags(struct kvm_vm *vm, uint32_t slot, uint32_t flags);
 void vm_mem_region_move(struct kvm_vm *vm, uint32_t slot, uint64_t new_gpa);
 void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot);
+int vm_mem_region_get_src_fd(struct kvm_vm *vm, uint32_t memslot);
 struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id);
 vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
 vm_vaddr_t vm_vaddr_alloc_pages(struct kvm_vm *vm, int nr_pages);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 3e45e3776bdf..7c81028f23d8 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -466,6 +466,29 @@ kvm_userspace_memory_region_find(struct kvm_vm *vm, uint64_t start,
 	return &region->region;
 }
 
+/*
+ * KVM Userspace Memory Get Backing Source FD
+ *
+ * Input Args:
+ *   vm - Virtual Machine
+ *   memslot - KVM memory slot ID
+ *
+ * Output Args: None
+ *
+ * Return:
+ *   Backing source file descriptor, -1 if the memslot is an anonymous region.
+ *
+ * Returns the backing source fd of a memslot, so tests can use it to punch
+ * holes, or to setup permissions.
+ */
+int vm_mem_region_get_src_fd(struct kvm_vm *vm, uint32_t memslot)
+{
+	struct userspace_mem_region *region;
+
+	region = memslot2region(vm, memslot);
+	return region->fd;
+}
+
 /*
  * VM VCPU Remove
  *
-- 
2.37.0.rc0.161.g10f37bed90-goog