[PATCH 2/3] KVM: arm64: selftests: fix thread migration in arch_timer_edge_cases

Sebastian Ott
2025-05-09T14:33:32Z

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 <sebott@redhat.com>
---
tools/testing/selftests/kvm/arm64/arch_timer_edge_cases.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/arch_timer_edge_cases.c b/tools/testing/selftests/kvm/arm64/arch_timer_edge_cases.c
index c4716e0c1438..a813b4c6c817 100644
--- a/tools/testing/selftests/kvm/arm64/arch_timer_edge_cases.c
+++ b/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);
--
2.49.0