KVM: arm64: selftests: Fix thread migration in arch_timer_edge_cases

arch_timer_edge_cases tries to migrate itself across host cpus. Before
the first test, it migrates to cpu 0 by setting up an affinity mask with
only bit 0 set. After that it looks for the next possible cpu in the
current affinity mask which still has only bit 0 set. So there is no
migration at all.

Fix this by reading the default mask at start and use this to find
the next cpu in each iteration.

Signed-off-by: Sebastian Ott <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Marc Zyngier <[email protected]>

Author: Sebastian Ott

tools/testing/selftests/kvm/arm64/arch_timer_edge_cases.c

@@ -849,17 +849,17 @@ static void guest_code(enum arch_timer timer)
 	GUEST_DONE();
 }
 
+static cpu_set_t default_cpuset;
+
 static uint32_t next_pcpu(void)
 {
 	uint32_t max = get_nprocs();
 	uint32_t cur = sched_getcpu();
 	uint32_t next = cur;
-	cpu_set_t cpuset;
+	cpu_set_t cpuset = default_cpuset;
 
 	TEST_ASSERT(max > 1, "Need at least two physical cpus");
 
-	sched_getaffinity(0, sizeof(cpuset), &cpuset);
-
 	do {
 		next = (next + 1) % CPU_SETSIZE;
 	} while (!CPU_ISSET(next, &cpuset));
@@ -1046,6 +1046,8 @@ int main(int argc, char *argv[])
 	if (!parse_args(argc, argv))
 		exit(KSFT_SKIP);
 
+	sched_getaffinity(0, sizeof(default_cpuset), &default_cpuset);
+
 	if (test_args.test_virtual) {
 		test_vm_create(&vm, &vcpu, VIRTUAL);
 		test_run(vm, vcpu);