Re: [PATCH v4 15/15] KVM: riscv: selftests: Add a test for counter overflow

[Anup Patel <anup@brainfault.org>]

On Thu, Feb 29, 2024 at 6:32 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> Add a test for verifying overflow interrupt. Currently, it relies on
> overflow support on cycle/instret events. This test works for cycle/
> instret events which support sampling via hpmcounters on the platform.
> There are no ISA extensions to detect if a platform supports that. Thus,
> this test will fail on platform with virtualization but doesn't
> support overflow on these two events.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>  tools/testing/selftests/kvm/riscv/sbi_pmu.c | 126 +++++++++++++++++++-
>  1 file changed, 125 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/riscv/sbi_pmu.c b/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> index 8ea2a6db6610..c0264c636054 100644
> --- a/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> +++ b/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> @@ -8,6 +8,7 @@
>   * Copyright (c) 2024, Rivos Inc.
>   */
>
> +#include "asm/csr.h"
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <string.h>
> @@ -16,6 +17,7 @@
>  #include "kvm_util.h"
>  #include "test_util.h"
>  #include "processor.h"
> +#include "arch_timer.h"
>
>  /* Maximum counters (firmware + hardware)*/
>  #define RISCV_MAX_PMU_COUNTERS 64
> @@ -26,6 +28,11 @@ union sbi_pmu_ctr_info ctrinfo_arr[RISCV_MAX_PMU_COUNTERS];
>  static void *snapshot_gva;
>  static vm_paddr_t snapshot_gpa;
>
> +static int pmu_irq = IRQ_PMU_OVF;
> +
> +static int vcpu_shared_irq_count;
> +static int counter_in_use;
> +
>  /* Cache the available counters in a bitmask */
>  static unsigned long counter_mask_available;
>
> @@ -69,7 +76,9 @@ unsigned long pmu_csr_read_num(int csr_num)
>  #undef switchcase_csr_read
>  }
>
> -static inline void dummy_func_loop(int iter)
> +static void stop_counter(unsigned long counter, unsigned long stop_flags);
> +
> +static inline void dummy_func_loop(uint64_t iter)
>  {
>         int i = 0;
>
> @@ -88,6 +97,26 @@ static void guest_illegal_exception_handler(struct ex_regs *regs)
>         regs->epc += 4;
>  }
>
> +static void guest_irq_handler(struct ex_regs *regs)
> +{
> +       unsigned int irq_num = regs->cause & ~CAUSE_IRQ_FLAG;
> +       struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
> +       unsigned long overflown_mask;
> +
> +       /* Stop all counters first to avoid further interrupts */
> +       sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_STOP, 0, 1UL << counter_in_use,
> +                 SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT, 0, 0, 0);
> +
> +       csr_clear(CSR_SIP, BIT(pmu_irq));
> +
> +       overflown_mask = READ_ONCE(snapshot_data->ctr_overflow_mask);
> +       GUEST_ASSERT(overflown_mask & (1UL << counter_in_use));
> +
> +       /* Validate that we are in the correct irq handler */
> +       GUEST_ASSERT_EQ(irq_num, pmu_irq);
> +       WRITE_ONCE(vcpu_shared_irq_count, vcpu_shared_irq_count+1);
> +}
> +
>  static unsigned long get_counter_index(unsigned long cbase, unsigned long cmask,
>                                        unsigned long cflags,
>                                        unsigned long event)
> @@ -263,6 +292,32 @@ static void test_pmu_event_snapshot(unsigned long event)
>         stop_counter(counter, SBI_PMU_STOP_FLAG_RESET);
>  }
>
> +static void test_pmu_event_overflow(unsigned long event)
> +{
> +       unsigned long counter;
> +       unsigned long counter_value_post;
> +       unsigned long counter_init_value = ULONG_MAX - 10000;
> +       struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
> +
> +       counter = get_counter_index(0, counter_mask_available, 0, event);
> +       counter_in_use = counter;
> +
> +       /* The counter value is updated w.r.t relative index of cbase passed to start/stop */
> +       WRITE_ONCE(snapshot_data->ctr_values[0], counter_init_value);
> +       start_counter(counter, SBI_PMU_START_FLAG_INIT_FROM_SNAPSHOT, 0);
> +       dummy_func_loop(10000);
> +       udelay(msecs_to_usecs(2000));
> +       /* irq handler should have stopped the counter */
> +
> +       counter_value_post = READ_ONCE(snapshot_data->ctr_values[counter_in_use]);
> +       /* The counter value after stopping should be less the init value due to overflow */
> +       __GUEST_ASSERT(counter_value_post < counter_init_value,
> +                      "counter_value_post %lx counter_init_value %lx for counter\n",
> +                      counter_value_post, counter_init_value);
> +
> +       stop_counter(counter, SBI_PMU_STOP_FLAG_RESET);
> +}
> +
>  static void test_invalid_event(void)
>  {
>         struct sbiret ret;
> @@ -361,6 +416,43 @@ static void test_pmu_events_snaphost(int cpu)
>         GUEST_DONE();
>  }
>
> +static void test_pmu_events_overflow(int cpu)
> +{
> +       long out_val = 0;
> +       bool probe;
> +       int num_counters = 0;
> +       unsigned long sbi_impl_version;
> +
> +       probe = guest_sbi_probe_extension(SBI_EXT_PMU, &out_val);
> +       GUEST_ASSERT(probe && out_val == 1);
> +
> +       sbi_impl_version = get_host_sbi_impl_version();
> +       if (sbi_impl_version >= sbi_mk_version(2, 0))
> +               __GUEST_ASSERT(0, "SBI implementation version doesn't support PMU Snapshot");
> +
> +       snapshot_set_shmem(snapshot_gpa, 0);
> +       csr_set(CSR_IE, BIT(pmu_irq));
> +       local_irq_enable();
> +
> +       /* Get the counter details */
> +       num_counters = get_num_counters();
> +       update_counter_info(num_counters);
> +
> +       /*
> +        * Qemu supports overflow for cycle/instruction.
> +        * This test may fail on any platform that do not support overflow for these two events.
> +        */
> +       test_pmu_event_overflow(SBI_PMU_HW_CPU_CYCLES);
> +       GUEST_ASSERT_EQ(vcpu_shared_irq_count, 1);
> +
> +       /* Renable the interrupt again for another event */
> +       csr_set(CSR_IE, BIT(pmu_irq));
> +       test_pmu_event_overflow(SBI_PMU_HW_INSTRUCTIONS);
> +       GUEST_ASSERT_EQ(vcpu_shared_irq_count, 2);
> +
> +       GUEST_DONE();
> +}
> +
>  static void run_vcpu(struct kvm_vcpu *vcpu)
>  {
>         struct ucall uc;
> @@ -449,6 +541,35 @@ static void test_vm_events_snapshot_test(void *guest_code)
>         test_vm_destroy(vm);
>  }
>
> +static void test_vm_events_overflow(void *guest_code)
> +{
> +       struct kvm_vm *vm = NULL;
> +       struct kvm_vcpu *vcpu = NULL;
> +
> +       vm = vm_create_with_one_vcpu(&vcpu, guest_code);
> +       __TEST_REQUIRE(__vcpu_has_ext(vcpu, RISCV_SBI_EXT_REG(KVM_RISCV_SBI_EXT_PMU)),
> +                                  "SBI PMU not available, skipping test");
> +
> +       __TEST_REQUIRE(__vcpu_has_ext(vcpu, RISCV_ISA_EXT_REG(KVM_RISCV_ISA_EXT_SSCOFPMF)),
> +                                  "Sscofpmf is not available, skipping overflow test");
> +
> +
> +       test_vm_setup_snapshot_mem(vm, vcpu);
> +       vm_init_vector_tables(vm);
> +       vm_install_interrupt_handler(vm, guest_irq_handler);
> +
> +       vcpu_init_vector_tables(vcpu);
> +       /* Initialize guest timer frequency. */
> +       vcpu_get_reg(vcpu, RISCV_TIMER_REG(frequency), &timer_freq);
> +       sync_global_to_guest(vm, timer_freq);
> +
> +       vcpu_args_set(vcpu, 1, 0);
> +
> +       run_vcpu(vcpu);
> +
> +       test_vm_destroy(vm);
> +}
> +
>  int main(void)
>  {
>         test_vm_basic_test(test_pmu_basic_sanity);
> @@ -460,5 +581,8 @@ int main(void)
>         test_vm_events_snapshot_test(test_pmu_events_snaphost);
>         pr_info("SBI PMU event verification with snapshot test : PASS\n");
>
> +       test_vm_events_overflow(test_pmu_events_overflow);
> +       pr_info("SBI PMU event verification with overflow test : PASS\n");
> +
>         return 0;
>  }
> --
> 2.34.1
>

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