|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v5 22/34] 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 NOT set (offsets differ)
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Assisted-by: Kiro (claude-opus-4.6-1m)
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../kvm/x86/masterclock_offset_test.c | 180 ++++++++++++++++++
2 files changed, 181 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 90568ab631d7..7ecaaf82056e 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -106,6 +106,7 @@ TEST_GEN_PROGS_x86 += x86/pmu_event_filter_test
TEST_GEN_PROGS_x86 += x86/private_mem_conversions_test
TEST_GEN_PROGS_x86 += x86/private_mem_kvm_exits_test
TEST_GEN_PROGS_x86 += x86/pvclock_test
+TEST_GEN_PROGS_x86 += x86/masterclock_offset_test
TEST_GEN_PROGS_x86 += x86/pvclock_migration_test
TEST_GEN_PROGS_x86 += x86/set_boot_cpu_id
TEST_GEN_PROGS_x86 += x86/set_sregs_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..88e2bd2edab5
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/masterclock_offset_test.c
@@ -0,0 +1,180 @@
+// 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 <stdint.h>
+#include <string.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#include <asm/pvclock-abi.h>
+
+#define KVMCLOCK_GPA 0xc0000000ull
+#define TSC_OFFSET (1000000000ULL)
+
+static uint64_t pvclock_calc(struct pvclock_vcpu_time_info *pvti, uint64_t
guest_tsc)
+{
+ uint64_t delta = guest_tsc - pvti->tsc_timestamp;
+
+ if (pvti->tsc_shift >= 0)
+ delta <<= pvti->tsc_shift;
+ else
+ delta >>= -(int)pvti->tsc_shift;
+
+ return pvti->system_time + ((__uint128_t)delta *
pvti->tsc_to_system_mul >> 32);
+}
+
+static void guest_code(void)
+{
+ wrmsr(MSR_KVM_SYSTEM_TIME_NEW, KVMCLOCK_GPA | KVM_MSR_ENABLED);
+ for (;;)
+ GUEST_SYNC(0);
+}
+
+int main(void)
+{
+ struct kvm_vcpu *vcpus[3];
+ struct kvm_clock_data clock;
+ struct pvclock_vcpu_time_info pvti[3];
+ struct kvm_vm *vm;
+ uint64_t offset0, host_tsc, clk0, clk2;
+ int i;
+
+ TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
+
+ vm = vm_create_with_vcpus(3, guest_code, vcpus);
+
+ TEST_REQUIRE(!__vcpu_has_device_attr(vcpus[0], KVM_VCPU_TSC_CTRL,
+ KVM_VCPU_TSC_OFFSET));
+
+ vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+ KVMCLOCK_GPA, 1,
+ vm_calc_num_guest_pages(VM_MODE_DEFAULT,
+ getpagesize()), 0);
+ virt_map(vm, KVMCLOCK_GPA, KVMCLOCK_GPA,
+ vm_calc_num_guest_pages(VM_MODE_DEFAULT, getpagesize()));
+
+ /* Get vCPU 0's default offset and set vCPU 2's offset higher */
+ vcpu_device_attr_get(vcpus[0], KVM_VCPU_TSC_CTRL,
+ KVM_VCPU_TSC_OFFSET, &offset0);
+ uint64_t offset2 = offset0 + TSC_OFFSET;
+ vcpu_device_attr_set(vcpus[2], KVM_VCPU_TSC_CTRL,
+ KVM_VCPU_TSC_OFFSET, &offset2);
+
+ /* Run each vCPU to enable kvmclock (with offset already set) */
+ for (i = 0; i < 3; i++) {
+ vcpu_run(vcpus[i]);
+ TEST_ASSERT_KVM_EXIT_REASON(vcpus[i], KVM_EXIT_IO);
+ }
+
+ /* Check master clock is active */
+ memset(&clock, 0, sizeof(clock));
+ vm_ioctl(vm, KVM_GET_CLOCK, &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);
+
+ /* Get per-vCPU pvclock in order 0, 2, 1 */
+ int order[] = {0, 2, 1};
+ for (i = 0; i < 3; i++) {
+ int idx = order[i];
+ __vcpu_ioctl(vcpus[idx], KVM_GET_CLOCK_GUEST, &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);
+ }
+
+ /* Read guest TSCs: should see (0+OFF) < 2 < (1+OFF) */
+ uint64_t gtsc0 = vcpu_get_msr(vcpus[0], MSR_IA32_TSC);
+ uint64_t gtsc2 = vcpu_get_msr(vcpus[2], MSR_IA32_TSC);
+ uint64_t 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);
+ pr_info("vcpu0+OFF=%lu vcpu1+OFF=%lu\n",
+ (unsigned long)(gtsc0 + TSC_OFFSET),
+ (unsigned long)(gtsc1 + TSC_OFFSET));
+ 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[2].tsc_to_system_mul &&
+ pvti[0].tsc_shift == pvti[2].tsc_shift,
+ "All vCPUs should have same mul/shift");
+
+ /*
+ * Read host TSC once. At this instant:
+ * vCPU 0 guest TSC = host_tsc + offset0
+ * vCPU 2 guest TSC = host_tsc + offset0 + TSC_OFFSET
+ * Feed each through its pvclock. Expect the same kvmclock.
+ */
+ host_tsc = rdtsc();
+ clk0 = pvclock_calc(&pvti[0], host_tsc + offset0);
+ clk2 = pvclock_calc(&pvti[2], host_tsc + offset0 + TSC_OFFSET);
+
+ pr_info("kvmclock via vCPU 0: %lu ns\n", (unsigned long)clk0);
+ pr_info("kvmclock via vCPU 2: %lu ns\n", (unsigned long)clk2);
+ TEST_ASSERT(clk0 == clk2,
+ "kvmclock from offset vCPUs should match exactly, "
+ "diff=%ld ns", (long)(clk2 - clk0));
+
+ pr_info("PASSED: pvclock consistent across offset vCPUs\n");
+
+ /*
+ * Now 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.
+ */
+ {
+#define ONE_HOUR_NS (3600ULL * NSEC_PER_SEC)
+ struct kvm_clock_data setclk = { .clock = clock.clock +
ONE_HOUR_NS };
+
+ vm_ioctl(vm, KVM_SET_CLOCK, &setclk);
+ }
+
+ /* Guest code does GUEST_SYNC then exits — run each to see update */
+ for (i = 0; i < 3; i++) {
+ vcpu_run(vcpus[order[i]]);
+ TEST_ASSERT_KVM_EXIT_REASON(vcpus[order[i]], KVM_EXIT_IO);
+ }
+
+ /* Re-read pvclocks */
+ for (i = 0; i < 3; i++)
+ __vcpu_ioctl(vcpus[order[i]], KVM_GET_CLOCK_GUEST,
&pvti[order[i]]);
+
+ pr_info("After +1h: vCPU 0 system_time=%lu, vCPU 2 system_time=%lu\n",
+ (unsigned long)pvti[0].system_time,
+ (unsigned long)pvti[2].system_time);
+ TEST_ASSERT(pvti[0].system_time == pvti[2].system_time,
+ "system_time should still match after KVM_SET_CLOCK");
+
+ host_tsc = rdtsc();
+ clk0 = pvclock_calc(&pvti[0], host_tsc + offset0);
+ clk2 = pvclock_calc(&pvti[2], host_tsc + offset0 + TSC_OFFSET);
+
+ pr_info("After +1h: kvmclock via vCPU 0: %lu ns\n", (unsigned
long)clk0);
+ pr_info("After +1h: kvmclock via vCPU 2: %lu ns\n", (unsigned
long)clk2);
+ TEST_ASSERT(clk0 == clk2,
+ "After +1h: kvmclock should still match, diff=%ld ns",
+ (long)(clk2 - clk0));
+
+ /* Verify the clock actually moved by ~1 hour */
+ TEST_ASSERT(clk0 > ONE_HOUR_NS,
+ "Clock should be > 1 hour after set, got %lu ns",
+ (unsigned long)clk0);
+
+ pr_info("PASSED: pvclock still consistent after KVM_SET_CLOCK +1h\n");
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.54.0
|
 |
Lists.xenproject.org is hosted with RackSpace, monitoring our |