KVM: x86: Test case for TSC scaling and offset sync

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20220225145304.36166-4-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/Makefile

@@ -66,6 +66,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/state_test
 TEST_GEN_PROGS_x86_64 += x86_64/vmx_preemption_timer_test
 TEST_GEN_PROGS_x86_64 += x86_64/svm_vmcall_test
 TEST_GEN_PROGS_x86_64 += x86_64/svm_int_ctl_test
+TEST_GEN_PROGS_x86_64 += x86_64/tsc_scaling_sync
 TEST_GEN_PROGS_x86_64 += x86_64/sync_regs_test
 TEST_GEN_PROGS_x86_64 += x86_64/userspace_io_test
 TEST_GEN_PROGS_x86_64 += x86_64/userspace_msr_exit_test

tools/testing/selftests/kvm/x86_64/tsc_scaling_sync.c

@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * svm_vmcall_test
+ *
+ * Copyright © 2021 Amazon.com, Inc. or its affiliates.
+ *
+ * Xen shared_info / pvclock testing
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#include <stdint.h>
+#include <time.h>
+#include <sched.h>
+#include <signal.h>
+#include <pthread.h>
+
+#define NR_TEST_VCPUS 20
+
+static struct kvm_vm *vm;
+pthread_spinlock_t create_lock;
+
+#define TEST_TSC_KHZ    2345678UL
+#define TEST_TSC_OFFSET 200000000
+
+uint64_t tsc_sync;
+static void guest_code(void)
+{
+	uint64_t start_tsc, local_tsc, tmp;
+
+	start_tsc = rdtsc();
+	do {
+		tmp = READ_ONCE(tsc_sync);
+		local_tsc = rdtsc();
+		WRITE_ONCE(tsc_sync, local_tsc);
+		if (unlikely(local_tsc < tmp))
+			GUEST_SYNC_ARGS(0, local_tsc, tmp, 0, 0);
+
+	} while (local_tsc - start_tsc < 5000 * TEST_TSC_KHZ);
+
+	GUEST_DONE();
+}
+
+
+static void *run_vcpu(void *_cpu_nr)
+{
+	unsigned long cpu = (unsigned long)_cpu_nr;
+	unsigned long failures = 0;
+	static bool first_cpu_done;
+
+	/* The kernel is fine, but vm_vcpu_add_default() needs locking */
+	pthread_spin_lock(&create_lock);
+
+	vm_vcpu_add_default(vm, cpu, guest_code);
+
+	if (!first_cpu_done) {
+		first_cpu_done = true;
+		vcpu_set_msr(vm, cpu, MSR_IA32_TSC, TEST_TSC_OFFSET);
+	}
+
+	pthread_spin_unlock(&create_lock);
+
+	for (;;) {
+		volatile struct kvm_run *run = vcpu_state(vm, cpu);
+                struct ucall uc;
+
+                vcpu_run(vm, cpu);
+                TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+                            "Got exit_reason other than KVM_EXIT_IO: %u (%s)\n",
+                            run->exit_reason,
+                            exit_reason_str(run->exit_reason));
+
+                switch (get_ucall(vm, cpu, &uc)) {
+                case UCALL_DONE:
+			goto out;
+
+                case UCALL_SYNC:
+			printf("Guest %ld sync %lx %lx %ld\n", cpu, uc.args[2], uc.args[3], uc.args[2] - uc.args[3]);
+			failures++;
+			break;
+
+                default:
+                        TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+	}
+ out:
+	return (void *)failures;
+}
+
+int main(int argc, char *argv[])
+{
+        if (!kvm_check_cap(KVM_CAP_VM_TSC_CONTROL)) {
+		print_skip("KVM_CAP_VM_TSC_CONTROL not available");
+		exit(KSFT_SKIP);
+	}
+
+	vm = vm_create_default_with_vcpus(0, DEFAULT_STACK_PGS * NR_TEST_VCPUS, 0, guest_code, NULL);
+	vm_ioctl(vm, KVM_SET_TSC_KHZ, (void *) TEST_TSC_KHZ);
+
+	pthread_spin_init(&create_lock, PTHREAD_PROCESS_PRIVATE);
+	pthread_t cpu_threads[NR_TEST_VCPUS];
+	unsigned long cpu;
+	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++)
+		pthread_create(&cpu_threads[cpu], NULL, run_vcpu, (void *)cpu);
+
+	unsigned long failures = 0;
+	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++) {
+		void *this_cpu_failures;
+		pthread_join(cpu_threads[cpu], &this_cpu_failures);
+		failures += (unsigned long)this_cpu_failures;
+	}
+
+	TEST_ASSERT(!failures, "TSC sync failed");
+	pthread_spin_destroy(&create_lock);
+	kvm_vm_free(vm);
+	return 0;
+}