Re: [PATCH v5 22/22] KVM: riscv: selftests: Add a test for counter overflow

Atish Patra
2024-04-09T23:47:55Z

On 4/5/24 06:23, Andrew Jones wrote:
> On Wed, Apr 03, 2024 at 01:04:51AM -0700, Atish Patra 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.
>
> Maybe we should give the user a command line option to disable this test
> in case the platform they're testing doesn't support it but they want to
> run the rest of the tests without getting a FAIL.
>

Sure. I will add that option.

>>
>> Reviewed-by: Anup Patel <anup@brainfault.org>
>> Signed-off-by: Atish Patra <atishp@rivosinc.com>
>> ---
>> .../selftests/kvm/riscv/sbi_pmu_test.c | 114 ++++++++++++++++++
>> 1 file changed, 114 insertions(+)
>>
>> diff --git a/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c b/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
>> index 7d195be5c3d9..451db956b885 100644
>> --- a/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
>> +++ b/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
>> @@ -14,6 +14,7 @@
>> #include "test_util.h"
>> #include "processor.h"
>> #include "sbi.h"
>> +#include "arch_timer.h"
>>
>> /* Maximum counters(firmware + hardware) */
>> #define RISCV_MAX_PMU_COUNTERS 64
>> @@ -24,6 +25,9 @@ union sbi_pmu_ctr_info ctrinfo_arr[RISCV_MAX_PMU_COUNTERS];
>> static void *snapshot_gva;
>> static vm_paddr_t snapshot_gpa;
>>
>> +static int vcpu_shared_irq_count;
>> +static int counter_in_use;
>> +
>> /* Cache the available counters in a bitmask */
>> static unsigned long counter_mask_available;
>>
>> @@ -117,6 +121,31 @@ 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;
>> + unsigned long counter_val = 0;
>> +
>> + /* Validate that we are in the correct irq handler */
>> + GUEST_ASSERT_EQ(irq_num, IRQ_PMU_OVF);
>> +
>> + /* Stop all counters first to avoid further interrupts */
>> + stop_counter(counter_in_use, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
>> +
>> + csr_clear(CSR_SIP, BIT(IRQ_PMU_OVF));
>> +
>> + overflown_mask = READ_ONCE(snapshot_data->ctr_overflow_mask);
>> + GUEST_ASSERT(overflown_mask & 0x01);
>> +
>> + WRITE_ONCE(vcpu_shared_irq_count, vcpu_shared_irq_count+1);
>> +
>> + counter_val = READ_ONCE(snapshot_data->ctr_values[0]);
>> + /* Now start the counter to mimick the real driver behavior */
>> + start_counter(counter_in_use, SBI_PMU_START_FLAG_SET_INIT_VALUE, counter_val);
>> +}
>> +
>> static unsigned long get_counter_index(unsigned long cbase, unsigned long cmask,
>> unsigned long cflags,
>> unsigned long event)
>> @@ -276,6 +305,33 @@ static void test_pmu_event_snapshot(unsigned long event)
>> stop_reset_counter(counter, 0);
>> }
>>
>> +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_SNAPSHOT, 0);
>> + dummy_func_loop(10000);
>> + udelay(msecs_to_usecs(2000));
>> + /* irq handler should have stopped the counter */
>> + stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
>> +
>> + counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
>> + /* 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_reset_counter(counter, 0);
>> +}
>> +
>> static void test_invalid_event(void)
>> {
>> struct sbiret ret;
>> @@ -366,6 +422,34 @@ static void test_pmu_events_snaphost(void)
>> GUEST_DONE();
>> }
>>
>> +static void test_pmu_events_overflow(void)
>> +{
>> + int num_counters = 0;
>> +
>> + /* Verify presence of SBI PMU and minimum requrired SBI version */
>> + verify_sbi_requirement_assert();
>> +
>> + snapshot_set_shmem(snapshot_gpa, 0);
>> + csr_set(CSR_IE, BIT(IRQ_PMU_OVF));
>> + 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);
>> +
>> + 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;
>> @@ -451,6 +535,33 @@ 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;
>> +
>> + vm = vm_create_with_one_vcpu(&vcpu, guest_code);
>> + __TEST_REQUIRE(__vcpu_has_sbi_ext(vcpu, KVM_RISCV_SBI_EXT_PMU),
>> + "SBI PMU not available, skipping test");
>> +
>> + __TEST_REQUIRE(__vcpu_has_isa_ext(vcpu, KVM_RISCV_ISA_EXT_SSCOFPMF),
>> + "Sscofpmf is not available, skipping overflow test");
>> +
>> +
>
> extra blank line here
>

Fixed.

>> + 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);
>> +
>> + run_vcpu(vcpu);
>> +
>> + test_vm_destroy(vm);
>> +}
>> +
>> int main(void)
>> {
>> pr_info("SBI PMU basic test : starting\n");
>> @@ -463,5 +574,8 @@ 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
>>
>
> Other than the command line option idea,
>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>
> Thanks,
> drew