Re: [PATCH v8 22/24] KVM: riscv: selftests: Add a test for PMU snapshot functionality

[Muhammad Usama Anjum]

On 4/20/24 8:17 PM, Atish Patra 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.
> 
> Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
> Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
LGTM

Reviewed-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>

> ---
>  .../testing/selftests/kvm/include/riscv/sbi.h |  25 +++
>  .../selftests/kvm/lib/riscv/processor.c       |  12 ++
>  .../selftests/kvm/riscv/sbi_pmu_test.c        | 144 ++++++++++++++++++
>  3 files changed, 181 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/riscv/sbi.h b/tools/testing/selftests/kvm/include/riscv/sbi.h
> index 6675ca673c77..046b432ae896 100644
> --- a/tools/testing/selftests/kvm/include/riscv/sbi.h
> +++ b/tools/testing/selftests/kvm/include/riscv/sbi.h
> @@ -8,6 +8,12 @@
>  #ifndef SELFTEST_KVM_SBI_H
>  #define SELFTEST_KVM_SBI_H
>  
> +/* 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
> +
>  /* SBI return error codes */
>  #define SBI_SUCCESS				 0
>  #define SBI_ERR_FAILURE				-1
> @@ -33,6 +39,9 @@ enum sbi_ext_id {
>  };
>  
>  enum sbi_ext_base_fid {
> +	SBI_EXT_BASE_GET_SPEC_VERSION = 0,
> +	SBI_EXT_BASE_GET_IMP_ID,
> +	SBI_EXT_BASE_GET_IMP_VERSION,
>  	SBI_EXT_BASE_PROBE_EXT = 3,
>  };
>  enum sbi_ext_pmu_fid {
> @@ -60,6 +69,12 @@ 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;
> @@ -113,4 +128,14 @@ 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 & SBI_SPEC_VERSION_MINOR_MASK);
> +}
> +
> +unsigned long get_host_sbi_spec_version(void);
> +
>  #endif /* SELFTEST_KVM_SBI_H */
> diff --git a/tools/testing/selftests/kvm/lib/riscv/processor.c b/tools/testing/selftests/kvm/lib/riscv/processor.c
> index e8211f5d6863..ccb35573749c 100644
> --- a/tools/testing/selftests/kvm/lib/riscv/processor.c
> +++ b/tools/testing/selftests/kvm/lib/riscv/processor.c
> @@ -502,3 +502,15 @@ bool guest_sbi_probe_extension(int extid, long *out_val)
>  
>  	return true;
>  }
> +
> +unsigned long get_host_sbi_spec_version(void)
> +{
> +	struct sbiret ret;
> +
> +	ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_GET_SPEC_VERSION, 0,
> +		       0, 0, 0, 0, 0);
> +
> +	GUEST_ASSERT(!ret.error);
> +
> +	return ret.value;
> +}
> diff --git a/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c b/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
> index 7c81691e39c5..9002ff451abf 100644
> --- a/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
> +++ b/tools/testing/selftests/kvm/riscv/sbi_pmu_test.c
> @@ -19,6 +19,11 @@
>  #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		BIT(30)
> +static void *snapshot_gva;
> +static vm_paddr_t snapshot_gpa;
> +
>  /* Cache the available counters in a bitmask */
>  static unsigned long counter_mask_available;
>  
> @@ -186,6 +191,32 @@ static unsigned long read_counter(int idx, union sbi_pmu_ctr_info ctrinfo)
>  	return counter_val;
>  }
>  
> +static inline void verify_sbi_requirement_assert(void)
> +{
> +	long out_val = 0;
> +	bool probe;
> +
> +	probe = guest_sbi_probe_extension(SBI_EXT_PMU, &out_val);
> +	GUEST_ASSERT(probe && out_val == 1);
> +
> +	if (get_host_sbi_spec_version() < sbi_mk_version(2, 0))
> +		__GUEST_ASSERT(0, "SBI implementation version doesn't support PMU Snapshot");
> +}
> +
> +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;
> @@ -234,6 +265,59 @@ static void test_pmu_event(unsigned long event)
>  	stop_reset_counter(counter, 0);
>  }
>  
> +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,
> +		       "Event update verification failed: post [%lx] pre [%lx]\n",
> +		       counter_value_post, counter_value_pre);
> +
> +	/*
> +	 * We can't just update the counter without starting it.
> +	 * Do start/stop twice to simulate that by first initializing to a very
> +	 * high value and a low value after that.
> +	 */
> +	WRITE_ONCE(snapshot_data->ctr_values[0], ULONG_MAX/2);
> +	start_counter(counter, SBI_PMU_START_FLAG_INIT_SNAPSHOT, 0);
> +	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
> +	counter_value_pre = READ_ONCE(snapshot_data->ctr_values[0]);
> +
> +	WRITE_ONCE(snapshot_data->ctr_values[0], counter_init_value);
> +	start_counter(counter, SBI_PMU_START_FLAG_INIT_SNAPSHOT, 0);
> +	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
> +	counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
> +	__GUEST_ASSERT(counter_value_pre > counter_value_post,
> +		       "Counter reinitialization verification failed : post [%lx] 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_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,
> +		       "Event update verification failed: post [%lx] pre [%lx]\n",
> +		       counter_value_post, counter_init_value);
> +
> +	stop_reset_counter(counter, 0);
> +}
> +
>  static void test_invalid_event(void)
>  {
>  	struct sbiret ret;
> @@ -301,6 +385,34 @@ static void test_pmu_basic_sanity(void)
>  	GUEST_DONE();
>  }
>  
> +static void test_pmu_events_snaphost(void)
> +{
> +	int num_counters = 0;
> +	struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
> +	int i;
> +
> +	/* Verify presence of SBI PMU and minimum requrired SBI version */
> +	verify_sbi_requirement_assert();
> +
> +	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 & (BIT(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;
> @@ -357,6 +469,35 @@ 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)
> +{
> +	/* PMU Snapshot requires single page only */
> +	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, PMU_SNAPSHOT_GPA_BASE, 1, 1, 0);
> +	/* PMU_SNAPSHOT_GPA_BASE is identity mapped */
> +	virt_map(vm, PMU_SNAPSHOT_GPA_BASE, PMU_SNAPSHOT_GPA_BASE, 1);
> +
> +	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;
> +
> +	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_vm_setup_snapshot_mem(vm, vcpu);
> +
> +	run_vcpu(vcpu);
> +
> +	test_vm_destroy(vm);
> +}
> +
>  int main(void)
>  {
>  	test_vm_basic_test(test_pmu_basic_sanity);
> @@ -365,5 +506,8 @@ 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;
>  }

-- 
BR,
Muhammad Usama Anjum