Re: [PATCH v4 14/15] KVM: riscv: selftests: Add a test for PMU snapshot functionality

[Anup Patel <anup@brainfault.org>]

On Thu, Feb 29, 2024 at 6:32 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> Verify PMU snapshot functionality by setting up the shared memory
> correctly and reading the counter values from the shared memory
> instead of the CSR.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

LGTM.

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

Regards,
Anup

> ---
>  .../selftests/kvm/include/riscv/processor.h   |  25 ++++
>  .../selftests/kvm/lib/riscv/processor.c       |  12 ++
>  tools/testing/selftests/kvm/riscv/sbi_pmu.c   | 124 ++++++++++++++++++
>  3 files changed, 161 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/include/riscv/processor.h b/tools/testing/selftests/kvm/include/riscv/processor.h
> index a49a39c8e8d4..e114d039e87b 100644
> --- a/tools/testing/selftests/kvm/include/riscv/processor.h
> +++ b/tools/testing/selftests/kvm/include/riscv/processor.h
> @@ -173,6 +173,7 @@ enum sbi_ext_id {
>  };
>
>  enum sbi_ext_base_fid {
> +       SBI_EXT_BASE_GET_IMP_VERSION = 2,
>         SBI_EXT_BASE_PROBE_EXT = 3,
>  };
>
> @@ -201,6 +202,12 @@ union sbi_pmu_ctr_info {
>         };
>  };
>
> +struct riscv_pmu_snapshot_data {
> +       u64 ctr_overflow_mask;
> +       u64 ctr_values[64];
> +       u64 reserved[447];
> +};
> +
>  struct sbiret {
>         long error;
>         long value;
> @@ -247,6 +254,14 @@ enum sbi_pmu_ctr_type {
>  #define SBI_PMU_STOP_FLAG_RESET (1 << 0)
>  #define SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT BIT(1)
>
> +#define SBI_STA_SHMEM_DISABLE          -1
> +
> +/* SBI spec version fields */
> +#define SBI_SPEC_VERSION_DEFAULT       0x1
> +#define SBI_SPEC_VERSION_MAJOR_SHIFT   24
> +#define SBI_SPEC_VERSION_MAJOR_MASK    0x7f
> +#define SBI_SPEC_VERSION_MINOR_MASK    0xffffff
> +
>  struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
>                         unsigned long arg1, unsigned long arg2,
>                         unsigned long arg3, unsigned long arg4,
> @@ -254,6 +269,16 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
>
>  bool guest_sbi_probe_extension(int extid, long *out_val);
>
> +/* Make SBI version */
> +static inline unsigned long sbi_mk_version(unsigned long major,
> +                                           unsigned long minor)
> +{
> +       return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
> +               SBI_SPEC_VERSION_MAJOR_SHIFT) | minor;
> +}
> +
> +unsigned long get_host_sbi_impl_version(void);
> +
>  static inline void local_irq_enable(void)
>  {
>         csr_set(CSR_SSTATUS, SR_SIE);
> diff --git a/tools/testing/selftests/kvm/lib/riscv/processor.c b/tools/testing/selftests/kvm/lib/riscv/processor.c
> index ec66d331a127..b0162d923e38 100644
> --- a/tools/testing/selftests/kvm/lib/riscv/processor.c
> +++ b/tools/testing/selftests/kvm/lib/riscv/processor.c
> @@ -499,3 +499,15 @@ bool guest_sbi_probe_extension(int extid, long *out_val)
>
>         return true;
>  }
> +
> +unsigned long get_host_sbi_impl_version(void)
> +{
> +       struct sbiret ret;
> +
> +       ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_GET_IMP_VERSION, 0,
> +                      0, 0, 0, 0, 0);
> +
> +       GUEST_ASSERT(!ret.error);
> +
> +       return ret.value;
> +}
> diff --git a/tools/testing/selftests/kvm/riscv/sbi_pmu.c b/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> index fc1fc5eea99e..8ea2a6db6610 100644
> --- a/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> +++ b/tools/testing/selftests/kvm/riscv/sbi_pmu.c
> @@ -21,6 +21,11 @@
>  #define RISCV_MAX_PMU_COUNTERS 64
>  union sbi_pmu_ctr_info ctrinfo_arr[RISCV_MAX_PMU_COUNTERS];
>
> +/* Snapshot shared memory data */
> +#define PMU_SNAPSHOT_GPA_BASE          (1 << 30)
> +static void *snapshot_gva;
> +static vm_paddr_t snapshot_gpa;
> +
>  /* Cache the available counters in a bitmask */
>  static unsigned long counter_mask_available;
>
> @@ -173,6 +178,20 @@ static void stop_counter(unsigned long counter, unsigned long stop_flags)
>                                counter, ret.error);
>  }
>
> +static void snapshot_set_shmem(vm_paddr_t gpa, unsigned long flags)
> +{
> +       unsigned long lo = (unsigned long)gpa;
> +#if __riscv_xlen == 32
> +       unsigned long hi = (unsigned long)(gpa >> 32);
> +#else
> +       unsigned long hi = gpa == -1 ? -1 : 0;
> +#endif
> +       struct sbiret ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_SNAPSHOT_SET_SHMEM,
> +                                     lo, hi, flags, 0, 0, 0);
> +
> +       GUEST_ASSERT(ret.value == 0 && ret.error == 0);
> +}
> +
>  static void test_pmu_event(unsigned long event)
>  {
>         unsigned long counter;
> @@ -207,6 +226,43 @@ static void test_pmu_event(unsigned long event)
>         stop_counter(counter, SBI_PMU_STOP_FLAG_RESET);
>  }
>
> +static void test_pmu_event_snapshot(unsigned long event)
> +{
> +       unsigned long counter;
> +       unsigned long counter_value_pre, counter_value_post;
> +       unsigned long counter_init_value = 100;
> +       struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
> +
> +       counter = get_counter_index(0, counter_mask_available, 0, event);
> +       counter_value_pre = read_counter(counter, ctrinfo_arr[counter]);
> +
> +       /* Do not set the initial value */
> +       start_counter(counter, 0, 0);
> +       dummy_func_loop(10000);
> +
> +       stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
> +
> +       /* The counter value is updated w.r.t relative index of cbase */
> +       counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
> +       __GUEST_ASSERT(counter_value_post > counter_value_pre,
> +                      "counter_value_post %lx counter_value_pre %lx\n",
> +                      counter_value_post, counter_value_pre);
> +
> +       /* Now set the initial value and compare */
> +       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);
> +
> +       stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
> +
> +       counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
> +       __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;
> @@ -270,6 +326,41 @@ static void test_pmu_basic_sanity(int cpu)
>         GUEST_DONE();
>  }
>
> +static void test_pmu_events_snaphost(int cpu)
> +{
> +       long out_val = 0;
> +       bool probe;
> +       int num_counters = 0;
> +       unsigned long sbi_impl_version;
> +       struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
> +       int i;
> +
> +       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);
> +
> +       /* Get the counter details */
> +       num_counters = get_num_counters();
> +       update_counter_info(num_counters);
> +
> +       /* Validate shared memory access */
> +       GUEST_ASSERT_EQ(READ_ONCE(snapshot_data->ctr_overflow_mask), 0);
> +       for (i = 0; i < num_counters; i++) {
> +               if (counter_mask_available & (1UL << i))
> +                       GUEST_ASSERT_EQ(READ_ONCE(snapshot_data->ctr_values[i]), 0);
> +       }
> +       /* Only these two events are guranteed to be present */
> +       test_pmu_event_snapshot(SBI_PMU_HW_CPU_CYCLES);
> +       test_pmu_event_snapshot(SBI_PMU_HW_INSTRUCTIONS);
> +
> +       GUEST_DONE();
> +}
> +
>  static void run_vcpu(struct kvm_vcpu *vcpu)
>  {
>         struct ucall uc;
> @@ -328,6 +419,36 @@ static void test_vm_events_test(void *guest_code)
>         test_vm_destroy(vm);
>  }
>
> +static void test_vm_setup_snapshot_mem(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
> +{
> +       vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, PMU_SNAPSHOT_GPA_BASE, 1, 1, 0);
> +       /* PMU Snapshot requires single page only */
> +       virt_map(vm, PMU_SNAPSHOT_GPA_BASE, PMU_SNAPSHOT_GPA_BASE, 1);
> +
> +       /* PMU_SNAPSHOT_GPA_BASE is identity mapped */
> +       snapshot_gva = (void *)(PMU_SNAPSHOT_GPA_BASE);
> +       snapshot_gpa = addr_gva2gpa(vcpu->vm, (vm_vaddr_t)snapshot_gva);
> +       sync_global_to_guest(vcpu->vm, snapshot_gva);
> +       sync_global_to_guest(vcpu->vm, snapshot_gpa);
> +}
> +
> +static void test_vm_events_snapshot_test(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_ISA_EXT_REG(KVM_RISCV_SBI_EXT_PMU)),
> +                                  "SBI PMU not available, skipping test");
> +
> +       test_vm_setup_snapshot_mem(vm, vcpu);
> +
> +       vcpu_args_set(vcpu, 1, 0);
> +       run_vcpu(vcpu);
> +
> +       test_vm_destroy(vm);
> +}
> +
>  int main(void)
>  {
>         test_vm_basic_test(test_pmu_basic_sanity);
> @@ -336,5 +457,8 @@ int main(void)
>         test_vm_events_test(test_pmu_events);
>         pr_info("SBI PMU event verification test : PASS\n");
>
> +       test_vm_events_snapshot_test(test_pmu_events_snaphost);
> +       pr_info("SBI PMU event verification with snapshot test : PASS\n");
> +
>         return 0;
>  }
> --
> 2.34.1
>

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