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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v13 20/26] KVM: selftests: Add master clock offset test
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
Verify that KVM master clock mode remains active when vCPUs have
different TSC offsets but the same frequency. Creates three vCPUs,
sets one to a different TSC value, and confirms:
- KVM_CLOCK_HOST_TSC is set (master clock active)
- KVM_CLOCK_TSC_STABLE IS set (master clock ⇒ stable flag)
- PVCLOCK_TSC_STABLE_BIT is NOT set (offsets differ)
Then set the KVM clock forward one hour with KVM_SET_CLOCK and verify
that all vCPUs still agree on the KVM clock computed from their own
pvclock parameters.
This remains a separate binary from pvclock_test deliberately: the
rdtsc()-plus-offset arithmetic here is exact only at the default host
frequency, while pvclock_test sweeps scaled frequencies, and the two
must not inherit each other's constraints.
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../kvm/x86/masterclock_offset_test.c | 249 ++++++++++++++++++
2 files changed, 250 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86/masterclock_offset_test.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm
b/tools/testing/selftests/kvm/Makefile.kvm
index 15a1a8f64723..4d4eff41c525 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -95,6 +95,7 @@ TEST_GEN_PROGS_x86 += x86/hyperv_tlb_flush
TEST_GEN_PROGS_x86 += x86/kvm_clock_test
TEST_GEN_PROGS_x86 += x86/kvm_pv_test
TEST_GEN_PROGS_x86 += x86/kvm_buslock_test
+TEST_GEN_PROGS_x86 += x86/masterclock_offset_test
TEST_GEN_PROGS_x86 += x86/monitor_mwait_test
TEST_GEN_PROGS_x86 += x86/msrs_test
TEST_GEN_PROGS_x86 += x86/nested_close_kvm_test
diff --git a/tools/testing/selftests/kvm/x86/masterclock_offset_test.c
b/tools/testing/selftests/kvm/x86/masterclock_offset_test.c
new file mode 100644
index 000000000000..7d0fe97cedc4
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/masterclock_offset_test.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test that KVM master clock mode works with different TSC offsets
+ * as long as all vCPUs have the same TSC frequency.
+ */
+#include <string.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#include <asm/pvclock.h>
+#include <asm/pvclock-abi.h>
+
+#define KVMCLOCK_GPA 0xc0000000ull
+#define TSC_OFFSET (1000000000ULL)
+
+#define NR_VCPUS 3
+
+/* Read the per-vCPU pvclocks in an order other than creation order. */
+static const int vcpu_order[NR_VCPUS] = {0, 2, 1};
+
+static void guest_code(u64 pvti_gpa)
+{
+ wrmsr(MSR_KVM_SYSTEM_TIME_NEW, pvti_gpa | KVM_MSR_ENABLED);
+ for (;;)
+ GUEST_SYNC(0);
+}
+
+static void get_pvtis(struct kvm_vcpu **vcpus,
+ struct pvclock_vcpu_time_info *pvti)
+{
+ int i;
+
+ for (i = 0; i < NR_VCPUS; i++) {
+ int idx = vcpu_order[i];
+
+ vcpu_get_clock_guest(vcpus[idx], &pvti[idx]);
+ pr_info("vCPU %d: tsc_timestamp=%lu system_time=%lu "
+ "mul=%u shift=%d flags=0x%x\n",
+ idx, (unsigned long)pvti[idx].tsc_timestamp,
+ (unsigned long)pvti[idx].system_time,
+ pvti[idx].tsc_to_system_mul, pvti[idx].tsc_shift,
+ pvti[idx].flags);
+ }
+}
+
+static void run_all_vcpus(struct kvm_vcpu **vcpus)
+{
+ int i;
+
+ for (i = 0; i < NR_VCPUS; i++) {
+ vcpu_run(vcpus[vcpu_order[i]]);
+ TEST_ASSERT_KVM_EXIT_REASON(vcpus[vcpu_order[i]], KVM_EXIT_IO);
+ }
+}
+
+/*
+ * The guest-visible pvclock pages must carry exactly what the ioctl
+ * reports: in master clock mode both are derived from the same master
+ * snapshot. Requires every vCPU to have run since the last masterclock
+ * update, so the pages are written from the settled snapshot.
+ */
+static void assert_guest_pages_match(struct kvm_vm *vm,
+ struct pvclock_vcpu_time_info *pvti,
+ const char *what)
+{
+ int i;
+
+ for (i = 0; i < NR_VCPUS; i++) {
+ struct pvclock_vcpu_time_info *guest_pvti =
+ addr_gpa2hva(vm, KVMCLOCK_GPA + i *
+ sizeof(struct pvclock_vcpu_time_info) * 2);
+
+ TEST_ASSERT(guest_pvti->tsc_timestamp == pvti[i].tsc_timestamp
&&
+ guest_pvti->system_time == pvti[i].system_time &&
+ guest_pvti->tsc_to_system_mul ==
pvti[i].tsc_to_system_mul &&
+ guest_pvti->tsc_shift == pvti[i].tsc_shift,
+ "%s: vCPU%d guest page pvclock should match
KVM_GET_CLOCK_GUEST",
+ what, i);
+ }
+}
+
+/*
+ * Read the host TSC once and feed it through each vCPU's pvclock
+ * (adding each vCPU's TSC offset). All must compute exactly the same
+ * kvmclock value.
+ */
+static void assert_pvclocks_match(struct pvclock_vcpu_time_info *pvti,
+ u64 offset0, const char *what)
+{
+ u64 host_tsc, clk0, clk1, clk2;
+
+ host_tsc = rdtsc();
+ clk0 = __pvclock_read_cycles(&pvti[0], host_tsc + offset0);
+ clk1 = __pvclock_read_cycles(&pvti[1], host_tsc + offset0);
+ clk2 = __pvclock_read_cycles(&pvti[2], host_tsc + offset0 + TSC_OFFSET);
+
+ pr_info("%s: kvmclock via vCPU 0: %lu ns, vCPU 1: %lu ns, vCPU 2: %lu
ns\n",
+ what, (unsigned long)clk0, (unsigned long)clk1,
+ (unsigned long)clk2);
+ TEST_ASSERT(clk0 == clk1 && clk0 == clk2,
+ "%s: kvmclock from all vCPUs should match exactly "
+ "(0: %lu, 1: %lu, 2: %lu)", what, (unsigned long)clk0,
+ (unsigned long)clk1, (unsigned long)clk2);
+}
+
+static void test_masterclock_active(struct kvm_vm *vm,
+ struct kvm_clock_data *clock)
+{
+ memset(clock, 0, sizeof(*clock));
+ vm_get_clock(vm, clock);
+ pr_info("KVM_GET_CLOCK flags: 0x%x\n", clock->flags);
+ TEST_ASSERT(clock->flags & KVM_CLOCK_HOST_TSC,
+ "Master clock should be active, flags=0x%x", clock->flags);
+ TEST_ASSERT(clock->flags & KVM_CLOCK_TSC_STABLE,
+ "KVM_CLOCK_TSC_STABLE should be set, flags=0x%x",
+ clock->flags);
+}
+
+static void test_offset_consistency(struct kvm_vcpu **vcpus,
+ struct pvclock_vcpu_time_info *pvti,
+ u64 offset0)
+{
+ u64 gtsc0, gtsc1, gtsc2;
+
+ get_pvtis(vcpus, pvti);
+
+ /* Read guest TSCs: should see (0+OFF) < 2 < (1+OFF) */
+ gtsc0 = vcpu_get_msr(vcpus[0], MSR_IA32_TSC);
+ gtsc2 = vcpu_get_msr(vcpus[2], MSR_IA32_TSC);
+ gtsc1 = vcpu_get_msr(vcpus[1], MSR_IA32_TSC);
+ pr_info("Guest TSCs: vcpu0=%lu vcpu2=%lu vcpu1=%lu\n",
+ (unsigned long)gtsc0, (unsigned long)gtsc2,
+ (unsigned long)gtsc1);
+ TEST_ASSERT(gtsc0 + TSC_OFFSET < gtsc2 && gtsc2 < gtsc1 + TSC_OFFSET,
+ "Expected (vcpu0+OFF) < vcpu2 < (vcpu1+OFF)");
+
+ /* PVCLOCK_TSC_STABLE_BIT should NOT be set (offsets differ) */
+ TEST_ASSERT(!(pvti[2].flags & PVCLOCK_TSC_STABLE_BIT),
+ "PVCLOCK_TSC_STABLE_BIT should NOT be set, flags=0x%x",
+ pvti[2].flags);
+
+ /* Same mul/shift */
+ TEST_ASSERT(pvti[0].tsc_to_system_mul == pvti[1].tsc_to_system_mul &&
+ pvti[0].tsc_to_system_mul == pvti[2].tsc_to_system_mul &&
+ pvti[0].tsc_shift == pvti[1].tsc_shift &&
+ pvti[0].tsc_shift == pvti[2].tsc_shift,
+ "All vCPUs should have same mul/shift");
+
+ assert_pvclocks_match(pvti, offset0, "Initial");
+}
+
+#define ONE_HOUR_NS (3600ULL * NSEC_PER_SEC)
+
+static void test_set_clock_consistency(struct kvm_vm *vm,
+ struct kvm_vcpu **vcpus,
+ struct pvclock_vcpu_time_info *pvti,
+ struct kvm_clock_data *clock,
+ u64 offset0)
+{
+ struct kvm_clock_data setclk = { .clock = clock->clock + ONE_HOUR_NS };
+ u64 clk0;
+
+ /*
+ * Add an hour to the VM kvmclock via KVM_SET_CLOCK, run each
+ * vCPU to pick up the update, and check they're still in sync.
+ */
+ vm_set_clock(vm, &setclk);
+
+ /*
+ * KVM_SET_CLOCK refreshes the master snapshot synchronously and
+ * broadcasts a clock update, so a single pass rewrites every
+ * guest pvclock page from the settled snapshot. Run two passes
+ * anyway, so this flow doesn't silently depend on that: after a
+ * per-vCPU write which parks a masterclock update on one vCPU
+ * (as the TSC-offset writes in main() do), the first pass
+ * services it and only the second rewrites every page.
+ */
+ run_all_vcpus(vcpus);
+ run_all_vcpus(vcpus);
+
+ get_pvtis(vcpus, pvti);
+ assert_guest_pages_match(vm, pvti, "After +1h");
+
+ TEST_ASSERT(pvti[0].system_time == pvti[1].system_time &&
+ pvti[0].system_time == pvti[2].system_time,
+ "system_time should still match after KVM_SET_CLOCK");
+
+ assert_pvclocks_match(pvti, offset0, "After +1h");
+
+ /* Verify the clock actually moved by ~1 hour */
+ clk0 = __pvclock_read_cycles(&pvti[0], rdtsc() + offset0);
+ TEST_ASSERT(clk0 > ONE_HOUR_NS,
+ "Clock should be > 1 hour after set, got %lu ns",
+ (unsigned long)clk0);
+}
+
+int main(void)
+{
+ struct pvclock_vcpu_time_info pvti[NR_VCPUS];
+ struct kvm_vcpu *vcpus[NR_VCPUS];
+ struct kvm_clock_data clock;
+ struct kvm_vm *vm;
+ u64 offset0;
+ int nr_pages;
+ int i;
+
+ TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
+ TEST_REQUIRE(kvm_has_cap(KVM_CAP_CLOCK_GUEST));
+
+ vm = vm_create_with_vcpus(NR_VCPUS, guest_code, vcpus);
+
+ TEST_REQUIRE(!__vcpu_has_device_attr(vcpus[0], KVM_VCPU_TSC_CTRL,
+ KVM_VCPU_TSC_OFFSET));
+
+ nr_pages = vm_calc_num_guest_pages(VM_MODE_DEFAULT, getpagesize());
+ vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+ KVMCLOCK_GPA, 1, nr_pages, 0);
+
+ /* Give each vCPU its own pvclock structure within the page */
+ for (i = 0; i < NR_VCPUS; i++)
+ vcpu_args_set(vcpus[i], 1, KVMCLOCK_GPA +
+ i * sizeof(struct pvclock_vcpu_time_info) * 2);
+
+ /* Get vCPU 0's default offset and set vCPU 2's offset higher */
+ offset0 = vcpu_get_tsc_offset(vcpus[0]);
+ vcpu_set_tsc_offset(vcpus[2], offset0 + TSC_OFFSET);
+
+ /*
+ * Run each vCPU twice to enable kvmclock (with the offset already
+ * set): the first pass services the masterclock update requested
+ * by the offset write, the second rewrites every guest pvclock
+ * page from the settled snapshot.
+ */
+ run_all_vcpus(vcpus);
+ run_all_vcpus(vcpus);
+
+ test_masterclock_active(vm, &clock);
+ test_offset_consistency(vcpus, pvti, offset0);
+ assert_guest_pages_match(vm, pvti, "Initial");
+ pr_info("PASSED: pvclock consistent across offset vCPUs\n");
+
+ test_set_clock_consistency(vm, vcpus, pvti, &clock, offset0);
+ pr_info("PASSED: pvclock still consistent after KVM_SET_CLOCK +1h\n");
+
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.43.0
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