selftests: KVM: Add test for KVM_{GET,SET}_CLOCK

Add a selftest for the new KVM clock UAPI that was introduced. Ensure
that the KVM clock is consistent between userspace and the guest, and
that the difference in realtime will only ever cause the KVM clock to
advance forward.

Cc: Andrew Jones <drjones@redhat.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181555.973085-3-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/.gitignore

@@ -12,6 +12,7 @@
 /x86_64/emulator_error_test
 /x86_64/get_cpuid_test
 /x86_64/get_msr_index_features
+/x86_64/kvm_clock_test
 /x86_64/kvm_pv_test
 /x86_64/hyperv_clock
 /x86_64/hyperv_cpuid

tools/testing/selftests/kvm/Makefile

@@ -46,6 +46,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/get_cpuid_test
 TEST_GEN_PROGS_x86_64 += x86_64/hyperv_clock
 TEST_GEN_PROGS_x86_64 += x86_64/hyperv_cpuid
 TEST_GEN_PROGS_x86_64 += x86_64/hyperv_features
+TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_test
 TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
 TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
 TEST_GEN_PROGS_x86_64 += x86_64/mmu_role_test

tools/testing/selftests/kvm/include/kvm_util.h

@@ -19,6 +19,8 @@
 #define KVM_DEV_PATH "/dev/kvm"
 #define KVM_MAX_VCPUS 512
 
+#define NSEC_PER_SEC 1000000000L
+
 /*
  * Callers of kvm_util only have an incomplete/opaque description of the
  * structure kvm_util is using to maintain the state of a VM.

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

@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021, Google LLC.
+ *
+ * Tests for adjusting the KVM clock from userspace
+ */
+#include <asm/kvm_para.h>
+#include <asm/pvclock.h>
+#include <asm/pvclock-abi.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <time.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#define VCPU_ID 0
+
+struct test_case {
+	uint64_t kvmclock_base;
+	int64_t realtime_offset;
+};
+
+static struct test_case test_cases[] = {
+	{ .kvmclock_base = 0 },
+	{ .kvmclock_base = 180 * NSEC_PER_SEC },
+	{ .kvmclock_base = 0, .realtime_offset = -180 * NSEC_PER_SEC },
+	{ .kvmclock_base = 0, .realtime_offset = 180 * NSEC_PER_SEC },
+};
+
+#define GUEST_SYNC_CLOCK(__stage, __val)			\
+		GUEST_SYNC_ARGS(__stage, __val, 0, 0, 0)
+
+static void guest_main(vm_paddr_t pvti_pa, struct pvclock_vcpu_time_info *pvti)
+{
+	int i;
+
+	wrmsr(MSR_KVM_SYSTEM_TIME_NEW, pvti_pa | KVM_MSR_ENABLED);
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++)
+		GUEST_SYNC_CLOCK(i, __pvclock_read_cycles(pvti, rdtsc()));
+}
+
+#define EXPECTED_FLAGS (KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC)
+
+static inline void assert_flags(struct kvm_clock_data *data)
+{
+	TEST_ASSERT((data->flags & EXPECTED_FLAGS) == EXPECTED_FLAGS,
+		    "unexpected clock data flags: %x (want set: %x)",
+		    data->flags, EXPECTED_FLAGS);
+}
+
+static void handle_sync(struct ucall *uc, struct kvm_clock_data *start,
+			struct kvm_clock_data *end)
+{
+	uint64_t obs, exp_lo, exp_hi;
+
+	obs = uc->args[2];
+	exp_lo = start->clock;
+	exp_hi = end->clock;
+
+	assert_flags(start);
+	assert_flags(end);
+
+	TEST_ASSERT(exp_lo <= obs && obs <= exp_hi,
+		    "unexpected kvm-clock value: %"PRIu64" expected range: [%"PRIu64", %"PRIu64"]",
+		    obs, exp_lo, exp_hi);
+
+	pr_info("kvm-clock value: %"PRIu64" expected range [%"PRIu64", %"PRIu64"]\n",
+		obs, exp_lo, exp_hi);
+}
+
+static void handle_abort(struct ucall *uc)
+{
+	TEST_FAIL("%s at %s:%ld", (const char *)uc->args[0],
+		  __FILE__, uc->args[1]);
+}
+
+static void setup_clock(struct kvm_vm *vm, struct test_case *test_case)
+{
+	struct kvm_clock_data data;
+
+	memset(&data, 0, sizeof(data));
+
+	data.clock = test_case->kvmclock_base;
+	if (test_case->realtime_offset) {
+		struct timespec ts;
+		int r;
+
+		data.flags |= KVM_CLOCK_REALTIME;
+		do {
+			r = clock_gettime(CLOCK_REALTIME, &ts);
+			if (!r)
+				break;
+		} while (errno == EINTR);
+
+		TEST_ASSERT(!r, "clock_gettime() failed: %d\n", r);
+
+		data.realtime = ts.tv_sec * NSEC_PER_SEC;
+		data.realtime += ts.tv_nsec;
+		data.realtime += test_case->realtime_offset;
+	}
+
+	vm_ioctl(vm, KVM_SET_CLOCK, &data);
+}
+
+static void enter_guest(struct kvm_vm *vm)
+{
+	struct kvm_clock_data start, end;
+	struct kvm_run *run;
+	struct ucall uc;
+	int i, r;
+
+	run = vcpu_state(vm, VCPU_ID);
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		setup_clock(vm, &test_cases[i]);
+
+		vm_ioctl(vm, KVM_GET_CLOCK, &start);
+
+		r = _vcpu_run(vm, VCPU_ID);
+		vm_ioctl(vm, KVM_GET_CLOCK, &end);
+
+		TEST_ASSERT(!r, "vcpu_run failed: %d\n", r);
+		TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+			    "unexpected exit reason: %u (%s)",
+			    run->exit_reason, exit_reason_str(run->exit_reason));
+
+		switch (get_ucall(vm, VCPU_ID, &uc)) {
+		case UCALL_SYNC:
+			handle_sync(&uc, &start, &end);
+			break;
+		case UCALL_ABORT:
+			handle_abort(&uc);
+			return;
+		default:
+			TEST_ASSERT(0, "unhandled ucall: %ld\n", uc.cmd);
+		}
+	}
+}
+
+#define CLOCKSOURCE_PATH "/sys/devices/system/clocksource/clocksource0/current_clocksource"
+
+static void check_clocksource(void)
+{
+	char *clk_name;
+	struct stat st;
+	FILE *fp;
+
+	fp = fopen(CLOCKSOURCE_PATH, "r");
+	if (!fp) {
+		pr_info("failed to open clocksource file: %d; assuming TSC.\n",
+			errno);
+		return;
+	}
+
+	if (fstat(fileno(fp), &st)) {
+		pr_info("failed to stat clocksource file: %d; assuming TSC.\n",
+			errno);
+		goto out;
+	}
+
+	clk_name = malloc(st.st_size);
+	TEST_ASSERT(clk_name, "failed to allocate buffer to read file\n");
+
+	if (!fgets(clk_name, st.st_size, fp)) {
+		pr_info("failed to read clocksource file: %d; assuming TSC.\n",
+			ferror(fp));
+		goto out;
+	}
+
+	TEST_ASSERT(!strncmp(clk_name, "tsc\n", st.st_size),
+		    "clocksource not supported: %s", clk_name);
+out:
+	fclose(fp);
+}
+
+int main(void)
+{
+	vm_vaddr_t pvti_gva;
+	vm_paddr_t pvti_gpa;
+	struct kvm_vm *vm;
+	int flags;
+
+	flags = kvm_check_cap(KVM_CAP_ADJUST_CLOCK);
+	if (!(flags & KVM_CLOCK_REALTIME)) {
+		print_skip("KVM_CLOCK_REALTIME not supported; flags: %x",
+			   flags);
+		exit(KSFT_SKIP);
+	}
+
+	check_clocksource();
+
+	vm = vm_create_default(VCPU_ID, 0, guest_main);
+
+	pvti_gva = vm_vaddr_alloc(vm, getpagesize(), 0x10000);
+	pvti_gpa = addr_gva2gpa(vm, pvti_gva);
+	vcpu_args_set(vm, VCPU_ID, 2, pvti_gpa, pvti_gva);
+
+	enter_guest(vm);
+	kvm_vm_free(vm);
+}