tsc_scaling_sync.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright © 2021 Amazon.com, Inc. or its affiliates.
  4 */
  5
  6#include "test_util.h"
  7#include "kvm_util.h"
  8#include "processor.h"
  9
 10#include <stdint.h>
 11#include <time.h>
 12#include <sched.h>
 13#include <signal.h>
 14#include <pthread.h>
 15
 16#define NR_TEST_VCPUS 20
 17
 18static struct kvm_vm *vm;
 19pthread_spinlock_t create_lock;
 20
 21#define TEST_TSC_KHZ    2345678UL
 22#define TEST_TSC_OFFSET 200000000
 23
 24uint64_t tsc_sync;
 25static void guest_code(void)
 26{
 27	uint64_t start_tsc, local_tsc, tmp;
 28
 29	start_tsc = rdtsc();
 30	do {
 31		tmp = READ_ONCE(tsc_sync);
 32		local_tsc = rdtsc();
 33		WRITE_ONCE(tsc_sync, local_tsc);
 34		if (unlikely(local_tsc < tmp))
 35			GUEST_SYNC_ARGS(0, local_tsc, tmp, 0, 0);
 36
 37	} while (local_tsc - start_tsc < 5000 * TEST_TSC_KHZ);
 38
 39	GUEST_DONE();
 40}
 41
 42
 43static void *run_vcpu(void *_cpu_nr)
 44{
 45	unsigned long vcpu_id = (unsigned long)_cpu_nr;
 46	unsigned long failures = 0;
 47	static bool first_cpu_done;
 48	struct kvm_vcpu *vcpu;
 49
 50	/* The kernel is fine, but vm_vcpu_add() needs locking */
 51	pthread_spin_lock(&create_lock);
 52
 53	vcpu = vm_vcpu_add(vm, vcpu_id, guest_code);
 54
 55	if (!first_cpu_done) {
 56		first_cpu_done = true;
 57		vcpu_set_msr(vcpu, MSR_IA32_TSC, TEST_TSC_OFFSET);
 58	}
 59
 60	pthread_spin_unlock(&create_lock);
 61
 62	for (;;) {
 63                struct ucall uc;
 64
 65		vcpu_run(vcpu);
 66		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
 67
 68		switch (get_ucall(vcpu, &uc)) {
 69                case UCALL_DONE:
 70			goto out;
 71
 72                case UCALL_SYNC:
 73			printf("Guest %d sync %lx %lx %ld\n", vcpu->id,
 74			       uc.args[2], uc.args[3], uc.args[2] - uc.args[3]);
 75			failures++;
 76			break;
 77
 78                default:
 79                        TEST_FAIL("Unknown ucall %lu", uc.cmd);
 80		}
 81	}
 82 out:
 83	return (void *)failures;
 84}
 85
 86int main(int argc, char *argv[])
 87{
 88	TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_TSC_CONTROL));
 89
 90	vm = vm_create(NR_TEST_VCPUS);
 91	vm_ioctl(vm, KVM_SET_TSC_KHZ, (void *) TEST_TSC_KHZ);
 92
 93	pthread_spin_init(&create_lock, PTHREAD_PROCESS_PRIVATE);
 94	pthread_t cpu_threads[NR_TEST_VCPUS];
 95	unsigned long cpu;
 96	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++)
 97		pthread_create(&cpu_threads[cpu], NULL, run_vcpu, (void *)cpu);
 98
 99	unsigned long failures = 0;
100	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++) {
101		void *this_cpu_failures;
102		pthread_join(cpu_threads[cpu], &this_cpu_failures);
103		failures += (unsigned long)this_cpu_failures;
104	}
105
106	TEST_ASSERT(!failures, "TSC sync failed");
107	pthread_spin_destroy(&create_lock);
108	kvm_vm_free(vm);
109	return 0;
110}