Re: [REPOST PATCH 14/16] selftests: KVM: aarch64: Add PMU test to chain all the counters

Reiji Watanabe
2023-03-08T03:40:49Z

Hi Raghu,

On Tue, Feb 14, 2023 at 5:07 PM Raghavendra Rao Ananta
<rananta@google.com> wrote:
>
> Extend the vCPU migration test to occupy all the vPMU counters,
> by configuring chained events on alternate counter-ids and chaining
> them with its corresponding predecessor counter, and verify against
> the extended behavior.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
> .../testing/selftests/kvm/aarch64/vpmu_test.c | 60 +++++++++++++++++++
> 1 file changed, 60 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/aarch64/vpmu_test.c b/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> index de725f4339ad5..fd00acb9391c8 100644
> --- a/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> +++ b/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> @@ -710,6 +710,63 @@ static void test_chained_count(int pmc_idx)
> pmu_irq_exit(chained_pmc_idx);
> }
>
> +static void test_chain_all_counters(void)
> +{
> + int i;
> + uint64_t cnt, pmcr_n = get_pmcr_n();
> + struct pmc_accessor *acc = &pmc_accessors[0];

How do you decide whether to test with all accessors ?
Perhaps, it might be simpler and more consistent if we implement each
test case with one specified accessor as an argument, and run those
test with each accessors?

> +
> + /*
> + * Test the occupancy of all the event counters, by chaining the
> + * alternate counters. The test assumes that the host hasn't
> + * occupied any counters. Hence, if the test fails, it could be
> + * because all the counters weren't available to the guest or
> + * there's actually a bug in KVM.
> + */
> +
> + /*
> + * Configure even numbered counters to count cpu-cycles, and chain
> + * each of them with its odd numbered counter.
> + */

You might want to use the cycle counter as well ?

Thank you,
Reiji

> + for (i = 0; i < pmcr_n; i++) {
> + if (i % 2) {
> + acc->write_typer(i, ARMV8_PMUV3_PERFCTR_CHAIN);
> + acc->write_cntr(i, 1);
> + } else {
> + pmu_irq_init(i);
> + acc->write_cntr(i, PRE_OVERFLOW_32);
> + acc->write_typer(i, ARMV8_PMUV3_PERFCTR_CPU_CYCLES);
> + }
> + enable_counter(i);
> + }
> +
> + /* Introduce some cycles */
> + execute_precise_instrs(500, ARMV8_PMU_PMCR_E);
> +
> + /*
> + * An overflow interrupt should've arrived for all the even numbered
> + * counters but none for the odd numbered ones. The odd numbered ones
> + * should've incremented exactly by 1.
> + */
> + for (i = 0; i < pmcr_n; i++) {
> + if (i % 2) {
> + GUEST_ASSERT_1(!pmu_irq_received(i), i);
> +
> + cnt = acc->read_cntr(i);
> + GUEST_ASSERT_2(cnt == 2, i, cnt);
> + } else {
> + GUEST_ASSERT_1(pmu_irq_received(i), i);
> + }
> + }
> +
> + /* Cleanup the states */
> + for (i = 0; i < pmcr_n; i++) {
> + if (i % 2 == 0)
> + pmu_irq_exit(i);
> + disable_counter(i);
> + }
> +}
> +
> static void test_event_count(uint64_t event, int pmc_idx, bool expect_count)
> {
> switch (event) {
> @@ -739,6 +796,9 @@ static void test_basic_pmu_functionality(void)
>
> /* Test chained events */
> test_chained_count(0);
> +
> + /* Test running chained events on all the implemented counters */
> + test_chain_all_counters();
> }
>
> /*
> --
> 2.39.1.581.gbfd45094c4-goog
>