There is kvmclock drift issue during the vCPU hotplug. It has been fixed by the commit c52ffadc65e2 ("KVM: x86: Don't unnecessarily force masterclock update on vCPU hotplug").
This is to add the test to verify if the master clock is updated when we write 0 to MSR_IA32_TSC from the host side.
Here is the usage example on the KVM with the bugfix reverted.
$ ./kvm_clock_drift -v -p 5 kvmclock based on old pvclock_vcpu_time_info: 5012221999 version: 2 tsc_timestamp: 3277968 system_time: 11849519 tsc_to_system_mul: 2152530255 tsc_shift: 0 flags: 1
kvmclock based on new pvclock_vcpu_time_info: 5012222411 version: 4 tsc_timestamp: 9980576184 system_time: 5012222411 tsc_to_system_mul: 2152530255 tsc_shift: 0 flags: 1
==== Test Assertion Failure ==== x86_64/kvm_clock_drift.c:216: clock_old == clock_new pid=14257 tid=14257 errno=4 - Interrupted system call 1 0x000000000040277b: main at kvm_clock_drift.c:216 2 0x00007f7766fa7e44: ?? ??:0 3 0x000000000040286d: _start at ??:? kvmclock drift detected, old=5012221999, new=5012222411
Signed-off-by: Dongli Zhang dongli.zhang@oracle.com --- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/x86_64/kvm_clock_drift.c | 223 ++++++++++++++++++ 2 files changed, 224 insertions(+) create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index 4412b42d95de..c665d0d8d348 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -84,6 +84,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/hyperv_features TEST_GEN_PROGS_x86_64 += x86_64/hyperv_ipi TEST_GEN_PROGS_x86_64 += x86_64/hyperv_svm_test TEST_GEN_PROGS_x86_64 += x86_64/hyperv_tlb_flush +TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_drift 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/monitor_mwait_test diff --git a/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c b/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c new file mode 100644 index 000000000000..324f0dbc5762 --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c @@ -0,0 +1,223 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * The kvmclock drift test. Emulate vCPU hotplug and online to verify if + * there is kvmclock drift. + * + * Adapted from steal_time.c + * + * Copyright (C) 2020, Red Hat, Inc. + * Copyright (C) 2024 Oracle and/or its affiliates. + */ + +#include <asm/kvm_para.h> +#include <asm/pvclock.h> +#include <asm/pvclock-abi.h> +#include <sys/stat.h> + +#include "kvm_util.h" +#include "processor.h" + +#define NR_VCPUS 2 +#define NR_SLOTS 2 +#define KVMCLOCK_SIZE sizeof(struct pvclock_vcpu_time_info) +/* + * KVMCLOCK_GPA is identity mapped + */ +#define KVMCLOCK_GPA (1 << 30) + +static uint64_t kvmclock_gpa = KVMCLOCK_GPA; + +static void guest_code(int cpu) +{ + struct pvclock_vcpu_time_info *kvmclock; + + /* + * vCPU#0 is to detect the change of pvclock_vcpu_time_info + */ + if (cpu == 0) { + GUEST_SYNC(0); + + kvmclock = (struct pvclock_vcpu_time_info *) kvmclock_gpa; + wrmsr(MSR_KVM_SYSTEM_TIME_NEW, kvmclock_gpa | KVM_MSR_ENABLED); + + /* + * Backup the pvclock_vcpu_time_info before vCPU#1 hotplug + */ + kvmclock[1] = kvmclock[0]; + + GUEST_SYNC(2); + /* + * Enter the guest to update pvclock_vcpu_time_info + */ + GUEST_SYNC(4); + } + + /* + * vCPU#1 is to emulate the vCPU hotplug + */ + if (cpu == 1) { + GUEST_SYNC(1); + /* + * This is after the host side MSR_IA32_TSC + */ + GUEST_SYNC(3); + } +} + +static void run_vcpu(struct kvm_vcpu *vcpu) +{ + struct ucall uc; + + vcpu_run(vcpu); + + switch (get_ucall(vcpu, &uc)) { + case UCALL_SYNC: + case UCALL_DONE: + break; + case UCALL_ABORT: + REPORT_GUEST_ASSERT(uc); + default: + TEST_ASSERT(false, "Unexpected exit: %s", + exit_reason_str(vcpu->run->exit_reason)); + } +} + +static void kvmclock_dump(struct pvclock_vcpu_time_info *kvmclock) +{ + pr_info(" version: %u\n", kvmclock->version); + pr_info(" tsc_timestamp: %lu\n", kvmclock->tsc_timestamp); + pr_info(" system_time: %lu\n", kvmclock->system_time); + pr_info(" tsc_to_system_mul: %u\n", kvmclock->tsc_to_system_mul); + pr_info(" tsc_shift: %d\n", kvmclock->tsc_shift); + pr_info(" flags: %u\n", kvmclock->flags); + pr_info("\n"); +} + +#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(int argc, char *argv[]) +{ + struct pvclock_vcpu_time_info *kvmclock; + struct kvm_vcpu *vcpus[NR_VCPUS]; + uint64_t clock_old, clock_new; + bool verbose = false; + unsigned int gpages; + struct kvm_vm *vm; + int period = 2; + uint64_t tsc; + int opt; + + check_clocksource(); + + while ((opt = getopt(argc, argv, "p:vh")) != -1) { + switch (opt) { + case 'p': + period = atoi_positive("The period (seconds) between vCPU hotplug", + optarg); + break; + case 'v': + verbose = true; + break; + case 'h': + default: + pr_info("usage: %s [-p period (seconds)] [-v]\n", argv[0]); + exit(1); + } + } + + vm = vm_create_with_vcpus(NR_VCPUS, guest_code, vcpus); + gpages = vm_calc_num_guest_pages(VM_MODE_DEFAULT, + KVMCLOCK_SIZE * NR_SLOTS); + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, + KVMCLOCK_GPA, 1, gpages, 0); + virt_map(vm, KVMCLOCK_GPA, KVMCLOCK_GPA, gpages); + + vcpu_args_set(vcpus[0], 1, 0); + vcpu_args_set(vcpus[1], 1, 1); + + /* + * Run vCPU#0 and vCPU#1 to update both pvclock_vcpu_time_info and + * master clock + */ + run_vcpu(vcpus[0]); + run_vcpu(vcpus[1]); + + /* + * Run vCPU#0 to backup the current pvclock_vcpu_time_info + */ + run_vcpu(vcpus[0]); + + sleep(period); + + /* + * Emulate the hotplug of vCPU#1 + */ + vcpu_set_msr(vcpus[1], MSR_IA32_TSC, 0); + + /* + * Emulate the online of vCPU#1 + */ + run_vcpu(vcpus[1]); + + /* + * Run vCPU#0 to backup the new pvclock_vcpu_time_info to detect + * if there is any change or kvmclock drift + */ + run_vcpu(vcpus[0]); + + kvmclock = addr_gva2hva(vm, kvmclock_gpa); + tsc = kvmclock[0].tsc_timestamp; + clock_old = __pvclock_read_cycles(&kvmclock[1], tsc); + clock_new = __pvclock_read_cycles(&kvmclock[0], tsc); + + if (verbose) { + pr_info("kvmclock based on old pvclock_vcpu_time_info: %lu\n", + clock_old); + kvmclock_dump(&kvmclock[1]); + pr_info("kvmclock based on new pvclock_vcpu_time_info: %lu\n", + clock_new); + kvmclock_dump(&kvmclock[0]); + } + + TEST_ASSERT(clock_old == clock_new, + "kvmclock drift detected, old=%lu, new=%lu", + clock_old, clock_new); + + kvm_vm_free(vm); + + return 0; +}
base-commit: f2a3fb7234e52f72ff4a38364dbf639cf4c7d6c6