[PATCH v2 07/12] selftests: KVM: Introduce system counter offset test

Oliver Upton
2021-07-16T21:26:51Z

Introduce a KVM selftest to verify that userspace manipulation of the
TSC (via the new vCPU attribute) results in the correct behavior within
the guest.

Signed-off-by: Oliver Upton <oupton@google.com>
---
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../kvm/system_counter_offset_test.c | 133 ++++++++++++++++++
3 files changed, 135 insertions(+)
create mode 100644 tools/testing/selftests/kvm/system_counter_offset_test.c

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index d0877d01e771..2752813d5090 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -50,3 +50,4 @@
/set_memory_region_test
/steal_time
/kvm_binary_stats_test
+/system_counter_offset_test
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index f7e24f334c6e..7bf2e5fb1d5a 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -83,6 +83,7 @@ TEST_GEN_PROGS_x86_64 += memslot_perf_test
TEST_GEN_PROGS_x86_64 += set_memory_region_test
TEST_GEN_PROGS_x86_64 += steal_time
TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
+TEST_GEN_PROGS_x86_64 += system_counter_offset_test

TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions
TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list
diff --git a/tools/testing/selftests/kvm/system_counter_offset_test.c b/tools/testing/selftests/kvm/system_counter_offset_test.c
new file mode 100644
index 000000000000..7e9015770759
--- /dev/null
+++ b/tools/testing/selftests/kvm/system_counter_offset_test.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021, Google LLC.
+ *
+ * Tests for adjusting the system counter from userspace
+ */
+#include <asm/kvm_para.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
+
+#ifdef __x86_64__
+
+struct test_case {
+ uint64_t tsc_offset;
+};
+
+static struct test_case test_cases[] = {
+ { 0 },
+ { 180 * NSEC_PER_SEC },
+ { -180 * NSEC_PER_SEC },
+};
+
+static void check_preconditions(struct kvm_vm *vm)
+{
+ if (!_vcpu_has_device_attr(vm, VCPU_ID, KVM_VCPU_TSC_CTRL, KVM_VCPU_TSC_OFFSET))
+ return;
+
+ print_skip("KVM_VCPU_TSC_OFFSET not supported; skipping test");
+ exit(KSFT_SKIP);
+}
+
+static void setup_system_counter(struct kvm_vm *vm, struct test_case *test)
+{
+ vcpu_access_device_attr(vm, VCPU_ID, KVM_VCPU_TSC_CTRL,
+ KVM_VCPU_TSC_OFFSET, &test->tsc_offset, true);
+}
+
+static uint64_t guest_read_system_counter(struct test_case *test)
+{
+ return rdtsc();
+}
+
+static uint64_t host_read_guest_system_counter(struct test_case *test)
+{
+ return rdtsc() + test->tsc_offset;
+}
+
+#else /* __x86_64__ */
+
+#error test not implemented for this architecture!
+
+#endif
+
+#define GUEST_SYNC_CLOCK(__stage, __val) \
+ GUEST_SYNC_ARGS(__stage, __val, 0, 0, 0)
+
+static void guest_main(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+ struct test_case *test = &test_cases[i];
+
+ GUEST_SYNC_CLOCK(i, guest_read_system_counter(test));
+ }
+
+ GUEST_DONE();
+}
+
+static void handle_sync(struct ucall *uc, uint64_t start, uint64_t end)
+{
+ uint64_t obs = uc->args[2];
+
+ TEST_ASSERT(start <= obs && obs <= end,
+ "unexpected system counter value: %"PRIu64" expected range: [%"PRIu64", %"PRIu64"]",
+ obs, start, end);
+
+ pr_info("system counter value: %"PRIu64" expected range [%"PRIu64", %"PRIu64"]\n",
+ obs, start, end);
+}
+
+static void handle_abort(struct ucall *uc)
+{
+ TEST_FAIL("%s at %s:%ld", (const char *)uc->args[0],
+ __FILE__, uc->args[1]);
+}
+
+static void enter_guest(struct kvm_vm *vm)
+{
+ uint64_t start, end;
+ struct ucall uc;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+ struct test_case *test = &test_cases[i];
+
+ setup_system_counter(vm, test);
+ start = host_read_guest_system_counter(test);
+ vcpu_run(vm, VCPU_ID);
+ end = host_read_guest_system_counter(test);
+
+ switch (get_ucall(vm, VCPU_ID, &uc)) {
+ case UCALL_SYNC:
+ handle_sync(&uc, start, end);
+ break;
+ case UCALL_ABORT:
+ handle_abort(&uc);
+ return;
+ case UCALL_DONE:
+ return;
+ }
+ }
+}
+
+int main(void)
+{
+ struct kvm_vm *vm;
+
+ vm = vm_create_default(VCPU_ID, 0, guest_main);
+ check_preconditions(vm);
+ ucall_init(vm, NULL);
+
+ enter_guest(vm);
+ kvm_vm_free(vm);
+}
--
2.32.0.402.g57bb445576-goog