Re: [PATCH v9 04/16] KVM: arm64: selftests: Test SET_NR_COUNTERS after first run

[Fuad Tabba]

On Mon, 20 Jul 2026 at 06:44, Akihiko Odaki
<odaki@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Add a regression test that runs one vCPU and then tries to change the
> VM-scoped PMU counter count through an idle sibling. Verify that
> SET_NR_COUNTERS fails with EBUSY once any vCPU has run.
>
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Akihiko Odaki <odaki@xxxxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>

Cheers,
/fuad

> ---
>  .../selftests/kvm/arm64/vpmu_counter_access.c      | 38 ++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> index 22223395969e..3b5bb421f401 100644
> --- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> +++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> @@ -461,6 +461,11 @@ static void run_vcpu(struct kvm_vcpu *vcpu, u64 pmcr_n)
>         }
>  }
>
> +static void guest_code_done(void)
> +{
> +       GUEST_DONE();
> +}
> +
>  static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters, bool expect_fail)
>  {
>         struct kvm_vcpu *vcpu;
> @@ -622,6 +627,37 @@ static bool kvm_supports_nr_counters_attr(void)
>         return supported;
>  }
>
> +static void test_set_nr_counters_after_vcpu_run(void)
> +{
> +       struct kvm_vcpu *running_vcpu, *stopped_vcpu;
> +       unsigned int nr_counters = 0;
> +       struct kvm_vcpu_init init;
> +       struct kvm_vm *vm;
> +       int ret;
> +       u64 irq = 23;
> +
> +       vm = vm_create(2);
> +       vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
> +       init.features[0] |= BIT(KVM_ARM_VCPU_PMU_V3);
> +       running_vcpu = aarch64_vcpu_add(vm, 0, &init, guest_code_done);
> +       stopped_vcpu = aarch64_vcpu_add(vm, 1, &init, guest_code_done);
> +       kvm_arch_vm_finalize_vcpus(vm);
> +
> +       vcpu_device_attr_set(running_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
> +                            KVM_ARM_VCPU_PMU_V3_IRQ, &irq);
> +       vcpu_device_attr_set(running_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
> +                            KVM_ARM_VCPU_PMU_V3_INIT, NULL);
> +       vcpu_run(running_vcpu);
> +
> +       ret = __vcpu_device_attr_set(stopped_vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
> +                                    KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS,
> +                                    &nr_counters);
> +       TEST_ASSERT(ret == -1 && errno == EBUSY,
> +                   KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
> +
> +       kvm_vm_free(vm);
> +}
> +
>  int main(void)
>  {
>         u64 i, pmcr_n;
> @@ -630,6 +666,8 @@ int main(void)
>         TEST_REQUIRE(kvm_supports_vgic_v3());
>         TEST_REQUIRE(kvm_supports_nr_counters_attr());
>
> +       test_set_nr_counters_after_vcpu_run();
> +
>         pmcr_n = get_pmcr_n_limit();
>         for (i = 0; i <= pmcr_n; i++) {
>                 run_access_test(i);
>
> --
> 2.55.0
>
>