Re: [PATCH v2 05/12] selftests: KVM: Add test for KVM_{GET,SET}_CLOCK

Andrew Jones
2021-07-21T14:59:03Z

On Fri, Jul 16, 2021 at 09:26:22PM +0000, Oliver Upton wrote:
> 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.
>
> Signed-off-by: Oliver Upton <oupton@google.com>
> ---
> tools/testing/selftests/kvm/.gitignore | 1 +
> tools/testing/selftests/kvm/Makefile | 1 +
> .../testing/selftests/kvm/include/kvm_util.h | 2 +
> .../selftests/kvm/x86_64/kvm_clock_test.c | 210 ++++++++++++++++++
> 4 files changed, 214 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
>
> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> index 06a351b4f93b..d0877d01e771 100644
> --- a/tools/testing/selftests/kvm/.gitignore
> +++ b/tools/testing/selftests/kvm/.gitignore
> @@ -11,6 +11,7 @@
> /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
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index b853be2ae3c6..f7e24f334c6e 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/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
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 010b59b13917..a8ac5d52e17b 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/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.
> diff --git a/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
> new file mode 100644
> index 000000000000..34c48f2dde54
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
> @@ -0,0 +1,210 @@
> +// 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()));
> + }
> +
> + GUEST_DONE();
> +}
> +
> +#define EXPECTED_FLAGS (KVM_CLOCK_REAL_TIME | 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_REAL_TIME;
> + 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;
> + case UCALL_DONE:
> + return;
> + }
> + }
> +}
> +
> +#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)
> +{
> + struct kvm_cpuid2 *best;
> + 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_REAL_TIME)) {
> + print_skip("KVM_CLOCK_REAL_TIME not supported; flags: %x",
> + flags);
> + exit(KSFT_SKIP);
> + }
> +
> + check_clocksource();
> +
> + vm = vm_create_default(VCPU_ID, 0, guest_main);
> +
> + best = kvm_get_supported_cpuid();
> + vcpu_set_cpuid(vm, VCPU_ID, best);

Default vm types (which use default vcpu types) will already set cpuids
like this for x86. See the bottom of
lib/x86_64/processor.c:vm_vcpu_add_default

Thanks,
drew

> +
> + 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);
> +}
> --
> 2.32.0.402.g57bb445576-goog
>
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