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

From: Andrew Jones
Date: Sat Mar 02 2024 - 07:13:19 EST

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On Wed, Feb 28, 2024 at 05:01:29PM -0800, 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.
>
> Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
> ---
> .../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

unrelated change

> +
> +/* 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;
> +}

We should probably just synch sbi.h into tools, since we need plenty
from it.

> +
> +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);

This function is almost identical to test_pmu_event(). If we change one,
we'll likely have to change the other. We should have a single function
which can be used by both tests. We can do that by passing a function
pointer for the read which is different for non-snapshot and snapshot.

> +}
> +
> 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)

unnecessary cpu parameter

> +{
> + 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))

BIT()

> + 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 */

This comment should go above the memory region add

> + virt_map(vm, PMU_SNAPSHOT_GPA_BASE, PMU_SNAPSHOT_GPA_BASE, 1);
> +
> + /* PMU_SNAPSHOT_GPA_BASE is identity mapped */

This comment should go above the virt_map

> + 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;

nit: no need to set to 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)),

RISCV_SBI_EXT_REG

> + "SBI PMU not available, skipping test");
> +
> + test_vm_setup_snapshot_mem(vm, vcpu);
> +
> + vcpu_args_set(vcpu, 1, 0);

no need to set args

> + 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
>

Thanks,
drew

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