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

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Message-ID: <CAAeT=Fyu6eoYX=1U1aXr5qrXSPmQdswcrE+Dz12SLK7R-1XDAQ@mail.gmail.com>
Date:   Tue, 7 Mar 2023 19:40:24 -0800
From:   Reiji Watanabe <reijiw@...gle.com>
To:     Raghavendra Rao Ananta <rananta@...gle.com>
Cc:     Oliver Upton <oupton@...gle.com>, Marc Zyngier <maz@...nel.org>,
        Ricardo Koller <ricarkol@...gle.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [REPOST PATCH 14/16] selftests: KVM: aarch64: Add PMU test to
 chain all the counters

Hi Raghu,

On Tue, Feb 14, 2023 at 5:07 PM Raghavendra Rao Ananta
<rananta@...gle.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@...gle.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
>