Hi Maxim, On 10/10/23 09:13, Maxim Levitsky wrote: > У пт, 2023-10-06 у 10:57 -0700, Dongli Zhang пише: >> As inspired by the discussion in [1], the boottime wallclock may drift due >> to the fact that the masterclock (or host monotonic clock) and kvmclock are >> calculated based on the algorithms in different domains. >> >> This is to introduce a testcase to print the boottime wallclock >> periodically to help diagnose the wallclock drift issue in the future. >> >> The idea is to wrmsr the MSR_KVM_WALL_CLOCK_NEW, and read the boottime >> wallclock nanoseconds immediately. >> >> References: >> [1] https://urldefense.com/v3/__https://lore.kernel.org/all/20231001111313.77586-1-nsaenz@amazon.com__;!!ACWV5N9M2RV99hQ!MOnoujF4PlfvZ3SUuyXgIpJC5mWiE5uLUsNW6AWgirGXcObN5uil_fnthRVcYaPA0N2uoNyLChBogHC7ZS6t$ >> >> Cc: David Woodhouse <dwmw@xxxxxxxxxxxx> >> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx> >> --- >> tools/testing/selftests/kvm/Makefile | 3 +- >> .../selftests/kvm/x86_64/boottime_wallclock.c | 100 ++++++++++++++++++ >> 2 files changed, 102 insertions(+), 1 deletion(-) >> create mode 100644 tools/testing/selftests/kvm/x86_64/boottime_wallclock.c >> >> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile >> index a3bb36fb3cfc..fea05b0118de 100644 >> --- a/tools/testing/selftests/kvm/Makefile >> +++ b/tools/testing/selftests/kvm/Makefile >> @@ -60,7 +60,8 @@ LIBKVM_riscv += lib/riscv/ucall.c >> TEST_PROGS_x86_64 += x86_64/nx_huge_pages_test.sh >> >> # Compiled test targets >> -TEST_GEN_PROGS_x86_64 = x86_64/cpuid_test >> +TEST_GEN_PROGS_x86_64 = x86_64/boottime_wallclock >> +TEST_GEN_PROGS_x86_64 += x86_64/cpuid_test >> TEST_GEN_PROGS_x86_64 += x86_64/cr4_cpuid_sync_test >> TEST_GEN_PROGS_x86_64 += x86_64/dirty_log_page_splitting_test >> TEST_GEN_PROGS_x86_64 += x86_64/get_msr_index_features >> diff --git a/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c b/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c >> new file mode 100644 >> index 000000000000..cc48c9b19920 >> --- /dev/null >> +++ b/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c >> @@ -0,0 +1,100 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * Copyright (C) 2023 Oracle and/or its affiliates. >> + */ >> + >> +#include <asm/kvm_para.h> >> +#include <asm/pvclock-abi.h> >> + >> +#include "kvm_util.h" >> +#include "processor.h" >> + >> +static int period = 10; >> + >> +#define GUEST_SYNC_WALLCLOCK(__stage, __val) \ >> + GUEST_SYNC_ARGS(__stage, __val, 0, 0, 0) >> + >> +static void guest_main(vm_paddr_t wc_pa, struct pvclock_wall_clock *wc) >> +{ >> + uint64_t wallclock; >> + >> + while (true) { >> + wrmsr(MSR_KVM_WALL_CLOCK_NEW, wc_pa); >> + >> + wallclock = wc->sec * NSEC_PER_SEC + wc->nsec; >> + >> + GUEST_SYNC_WALLCLOCK(0, wallclock); > > Won't this fill the output very fast? > Do you think it will be worth it to wait some time (e.g 1 second or at least 1/10 of a second) > between each print? The wait time is controlled by the VMM side (of selftest) as in below. In the while loop at VMM side, it sleeps for a period (configurable argument), until it runs into the guest again. Therefore, the user can decide the frequency to print the boottime wallclock. +static void enter_guest(struct kvm_vcpu *vcpu) +{ + struct ucall uc; + + while (true) { + vcpu_run(vcpu); -----------> to schedule guest vcpu here + + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO); + + switch (get_ucall(vcpu, &uc)) { + case UCALL_SYNC: + handle_sync(&uc); + break; + case UCALL_ABORT: + handle_abort(&uc); + return; + default: + TEST_ASSERT(0, "unhandled ucall: %ld\n", uc.cmd); + return; + } + + sleep(period); ------------> sleep here + } +} Thank you very much! Dongli Zhang > >> + } >> +} >> + >> +static void handle_sync(struct ucall *uc) >> +{ >> + uint64_t wallclock; >> + >> + wallclock = uc->args[2]; >> + >> + pr_info("Boottime wallclock value: %"PRIu64" ns\n", wallclock); >> +} >> + >> +static void handle_abort(struct ucall *uc) >> +{ >> + REPORT_GUEST_ASSERT(*uc); >> +} >> + >> +static void enter_guest(struct kvm_vcpu *vcpu) >> +{ >> + struct ucall uc; >> + >> + while (true) { >> + vcpu_run(vcpu); >> + >> + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO); >> + >> + switch (get_ucall(vcpu, &uc)) { >> + case UCALL_SYNC: >> + handle_sync(&uc); >> + break; >> + case UCALL_ABORT: >> + handle_abort(&uc); >> + return; >> + default: >> + TEST_ASSERT(0, "unhandled ucall: %ld\n", uc.cmd); >> + return; >> + } >> + >> + sleep(period); >> + } >> +} >> + >> +int main(int argc, char *argv[]) >> +{ >> + struct kvm_vcpu *vcpu; >> + struct kvm_vm *vm; >> + vm_vaddr_t wc_gva; >> + vm_paddr_t wc_gpa; >> + int opt; >> + >> + while ((opt = getopt(argc, argv, "p:h")) != -1) { >> + switch (opt) { >> + case 'p': >> + period = atoi_positive("The period (seconds)", optarg); >> + break; >> + case 'h': >> + default: >> + pr_info("usage: %s [-p period (seconds)]\n", argv[0]); >> + exit(1); >> + } >> + } >> + >> + pr_info("Capture boottime wallclock every %d seconds.\n", period); >> + pr_info("Stop with Ctrl + c.\n\n"); >> + >> + vm = vm_create_with_one_vcpu(&vcpu, guest_main); >> + >> + wc_gva = vm_vaddr_alloc(vm, getpagesize(), 0x10000); >> + wc_gpa = addr_gva2gpa(vm, wc_gva); >> + vcpu_args_set(vcpu, 2, wc_gpa, wc_gva); >> + >> + enter_guest(vcpu); >> + kvm_vm_free(vm); >> +} > > > Best regards, > Maxim Levitsky > >
