Re: [REPOST PATCH 13/16] selftests: KVM: aarch64: Test chained events for PMU

Reiji Watanabe
2023-03-08T03:15:49Z

HI Raghu,

On Tue, Feb 14, 2023 at 5:07 PM Raghavendra Rao Ananta
<rananta@google.com> wrote:
>
> Extend the vPMU's vCPU migration test to validate
> chained events, and their overflow conditions.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
> .../testing/selftests/kvm/aarch64/vpmu_test.c | 76 ++++++++++++++++++-
> 1 file changed, 75 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/aarch64/vpmu_test.c b/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> index 066dc17fa3906..de725f4339ad5 100644
> --- a/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> +++ b/tools/testing/selftests/kvm/aarch64/vpmu_test.c
> @@ -23,7 +23,7 @@
> * migrating the guest vCPU to random pCPUs in the system, and check
> * if the vPMU is still behaving as expected. The sub-tests include
> * testing basic functionalities such as basic counters behavior,
> - * overflow, and overflow interrupts.
> + * overflow, overflow interrupts, and chained events.
> *
> * Copyright (c) 2022 Google LLC.
> *
> @@ -61,6 +61,8 @@
> #define PRE_OVERFLOW_32 (GENMASK(31, 0) - COUNT_TO_OVERFLOW + 1)
> #define PRE_OVERFLOW_64 (GENMASK(63, 0) - COUNT_TO_OVERFLOW + 1)
>
> +#define ALL_SET_64 GENMASK(63, 0)
> +
> #define GICD_BASE_GPA 0x8000000ULL
> #define GICR_BASE_GPA 0x80A0000ULL
>
> @@ -639,6 +641,75 @@ static void test_cycles_count(bool expect_count, bool test_overflow)
> pmu_disable_reset();
> }
>
> +static void test_chained_count(int pmc_idx)
> +{
> + int i, chained_pmc_idx;
> + struct pmc_accessor *acc;
> + uint64_t pmcr_n, cnt, cntr_val;
> +
> + /* The test needs at least two PMCs */
> + pmcr_n = get_pmcr_n();
> + GUEST_ASSERT_1(pmcr_n >= 2, pmcr_n);

Nit: As the architecture doesn't require this, rather than causing the
test failure, I would suggest gracefully skipping this test case or
make this the requirement of the test.

Thanks,
Reiji

> +
> + /*
> + * The chained counter's idx is always chained with (pmc_idx + 1).
> + * pmc_idx should be even as the chained event doesn't count on
> + * odd numbered counters.
> + */
> + GUEST_ASSERT_1(pmc_idx % 2 == 0, pmc_idx);
> +
> + /*
> + * The max counter idx that the chained counter can occupy is
> + * (pmcr_n - 1), while the actual event sits on (pmcr_n - 2).
> + */
> + chained_pmc_idx = pmc_idx + 1;
> + GUEST_ASSERT(chained_pmc_idx < pmcr_n);
> +
> + enable_counter(chained_pmc_idx);
> + pmu_irq_init(chained_pmc_idx);
> +
> + /* Configure the chained event using all the possible ways*/
> + for (i = 0; i < ARRAY_SIZE(pmc_accessors); i++) {
> + acc = &pmc_accessors[i];
> +
> + /* Test if the chained counter increments when the base event overflows */
> +
> + cntr_val = 1;
> + acc->write_cntr(chained_pmc_idx, cntr_val);
> + acc->write_typer(chained_pmc_idx, ARMV8_PMUV3_PERFCTR_CHAIN);
> +
> + /* Chain the counter with pmc_idx that's configured for an overflow */
> + test_instructions_count(pmc_idx, true, true);
> +
> + /*
> + * pmc_idx is also configured to run for all the ARRAY_SIZE(pmc_accessors)
> + * combinations. Hence, the chained chained_pmc_idx is expected to be
> + * cntr_val + ARRAY_SIZE(pmc_accessors).
> + */
> + cnt = acc->read_cntr(chained_pmc_idx);
> + GUEST_ASSERT_4(cnt == cntr_val + ARRAY_SIZE(pmc_accessors),
> + pmc_idx, i, cnt, cntr_val + ARRAY_SIZE(pmc_accessors));
> +
> + /* Test for the overflow of the chained counter itself */
> +
> + cntr_val = ALL_SET_64;
> + acc->write_cntr(chained_pmc_idx, cntr_val);
> +
> + test_instructions_count(pmc_idx, true, true);
> +
> + /*
> + * At this point, an interrupt should've been fired for the chained
> + * counter (which validates the overflow bit), and the counter should've
> + * wrapped around to ARRAY_SIZE(pmc_accessors) - 1.
> + */
> + cnt = acc->read_cntr(chained_pmc_idx);
> + GUEST_ASSERT_4(cnt == ARRAY_SIZE(pmc_accessors) - 1,
> + pmc_idx, i, cnt, ARRAY_SIZE(pmc_accessors));
> + }
> +
> + pmu_irq_exit(chained_pmc_idx);
> +}
> +
> static void test_event_count(uint64_t event, int pmc_idx, bool expect_count)
> {
> switch (event) {
> @@ -665,6 +736,9 @@ static void test_basic_pmu_functionality(void)
> /* Test overflow with interrupts on generic and cycle counters */
> test_instructions_count(0, true, true);
> test_cycles_count(true, true);
> +
> + /* Test chained events */
> + test_chained_count(0);
> }
>
> /*
> --
> 2.39.1.581.gbfd45094c4-goog
>