KVM: selftests: allow different backing source types

Add an argument which lets us specify a different backing memory type
for the test. The default is just to use anonymous, matching existing
behavior.

This is in preparation for testing UFFD minor faults. For that, we'll
need to use a new backing memory type which is setup with MAP_SHARED.
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Message-Id: <20210519200339.829146-6-axelrasmussen@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/demand_paging_test.c

@@ -240,6 +240,7 @@ static void setup_demand_paging(struct kvm_vm *vm,
 struct test_params {
 	bool use_uffd;
 	useconds_t uffd_delay;
+	enum vm_mem_backing_src_type src_type;
 	bool partition_vcpu_memory_access;
 };
 
@@ -257,11 +258,11 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 	int r;
 
 	vm = perf_test_create_vm(mode, nr_vcpus, guest_percpu_mem_size,
-				 VM_MEM_SRC_ANONYMOUS);
+				 p->src_type);
 
 	perf_test_args.wr_fract = 1;
 
-	demand_paging_size = get_backing_src_pagesz(VM_MEM_SRC_ANONYMOUS);
+	demand_paging_size = get_backing_src_pagesz(p->src_type);
 
 	guest_data_prototype = malloc(demand_paging_size);
 	TEST_ASSERT(guest_data_prototype,
@@ -377,7 +378,7 @@ static void help(char *name)
 {
 	puts("");
 	printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n"
-	       "          [-b memory] [-v vcpus] [-o]\n", name);
+	       "          [-b memory] [-t type] [-v vcpus] [-o]\n", name);
 	guest_modes_help();
 	printf(" -u: use User Fault FD to handle vCPU page\n"
 	       "     faults.\n");
@@ -387,6 +388,8 @@ static void help(char *name)
 	printf(" -b: specify the size of the memory region which should be\n"
 	       "     demand paged by each vCPU. e.g. 10M or 3G.\n"
 	       "     Default: 1G\n");
+	printf(" -t: The type of backing memory to use. Default: anonymous\n");
+	backing_src_help();
 	printf(" -v: specify the number of vCPUs to run.\n");
 	printf(" -o: Overlap guest memory accesses instead of partitioning\n"
 	       "     them into a separate region of memory for each vCPU.\n");
@@ -398,13 +401,14 @@ int main(int argc, char *argv[])
 {
 	int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
 	struct test_params p = {
+		.src_type = VM_MEM_SRC_ANONYMOUS,
 		.partition_vcpu_memory_access = true,
 	};
 	int opt;
 
 	guest_modes_append_default();
 
-	while ((opt = getopt(argc, argv, "hm:ud:b:v:o")) != -1) {
+	while ((opt = getopt(argc, argv, "hm:ud:b:t:v:o")) != -1) {
 		switch (opt) {
 		case 'm':
 			guest_modes_cmdline(optarg);
@@ -419,6 +423,9 @@ int main(int argc, char *argv[])
 		case 'b':
 			guest_percpu_mem_size = parse_size(optarg);
 			break;
+		case 't':
+			p.src_type = parse_backing_src_type(optarg);
+			break;
 		case 'v':
 			nr_vcpus = atoi(optarg);
 			TEST_ASSERT(nr_vcpus > 0 && nr_vcpus <= max_vcpus,