From: David Woodhouse <[email protected]> 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 <[email protected]> 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
