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

[Atish Patra <atishp@rivosinc.com>]

On 3/2/24 04:13, Andrew Jones wrote:
> 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@rivosinc.com>
>> ---
>>   .../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
> 

Dropped it.

>> +
>> +/* 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.
> 

As of now I have created sbi.h and moved all the definitions there. 
There is a still lot of difference between sbi.h. Do we really want to 
bring everything in ? Should we adopt kvmtool like policy to sync sbi.h
or just do it as new test cases need sbi.h?

I can send another version with syncing sbi.h if you still think that's 
better.


>> +
>> +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.
> 

There are more difference than just read function. Stop/start takes 
snapshot specific flag. We also have to update the counter in the shared 
memory. If we combine the two functions to a single one, we will end up 
with bunch of if else condition which I don't like.

I am okay modifying it if you feel strongly about it though.

>> +}
>> +
>>   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
> 

Removed.

>> +{
>> +	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()
> 

Done.

>> +			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
> 

Fixed.

>> +	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
> 

Updated to use the new helper functions as suggested in the earlier patch.

>> +				   "SBI PMU not available, skipping test");
>> +
>> +	test_vm_setup_snapshot_mem(vm, vcpu);
>> +
>> +	vcpu_args_set(vcpu, 1, 0);
> 
> no need to set args
> 

Fixed.

>> +	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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