From patchwork Wed Mar 31 07:29:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Tzvetomir Stoyanov (VMware)" X-Patchwork-Id: 12174529 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76B4CC433E1 for ; Wed, 31 Mar 2021 07:30:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2FA78619D8 for ; Wed, 31 Mar 2021 07:30:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233881AbhCaH3j (ORCPT ); Wed, 31 Mar 2021 03:29:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233906AbhCaH3L (ORCPT ); Wed, 31 Mar 2021 03:29:11 -0400 Received: from mail-ej1-x62b.google.com (mail-ej1-x62b.google.com [IPv6:2a00:1450:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42A02C061574 for ; Wed, 31 Mar 2021 00:29:11 -0700 (PDT) Received: by mail-ej1-x62b.google.com with SMTP id u9so28518489ejj.7 for ; Wed, 31 Mar 2021 00:29:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=N+7EZVHy39sneOSePn8zq6QlkCdshLlo0tefSbuMm6A=; b=la3UH9ujVawyrF1PA5NfoZkdRKrKXOX8UrAqcpBL1H7mpauEV0VLTxwqSbPo68kCDg f3pus39ugEvl18YdTgvyqLYiHJPNQO8MMEqxyznL8CXs2Lzs1CIrd4Co4h0B9w60KO1h FZzHTVkMG4E5B2OcmGaDJtLYvBgfHDmIa/jzOWdWklw4vXXUL0dEToK7xnC1jWwoTJ9z ZAiPMAeJ1VHeNwBw21vF+MbIkOpXNMqf/dqA9lrDlvfy8Ixo41HyF2vk4DviVU74wzJg vsWsOxQnEWbS2yjxQs8WFSOELd6oompyh7HsU8Roji+SRc5Sj++57f94SVxQu1umA4JB CnGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=N+7EZVHy39sneOSePn8zq6QlkCdshLlo0tefSbuMm6A=; b=mG96ZNxRB/NWlaIYT45b9xkZFwgIoEiYYQI6XCjA++5vPbft8JLlhuXf5p5JIcEUD/ gUkPhzRALu6amqo3P0EfRw7iVLY65euzETRkvZezRgPOjImqiIWvp5GpZRm9PcOBM+pE 1fS5t635VAg1YGjZ2xbwV/gAP5R2rRIJbPCZxBr95M2Mle4oZTlLmfbvvGGMmhEGXims 5pW53oB4JC+JeVgTXf4uTakDk1xzLNc793ZKGg/HXvwYoPqnAX/bA6MNakjTdTj69ZFw 0L+ntua1zZVPA5wTbJKXx7riuBjx/HL0wUI+9n8iCTq+D2VgVlKGa/lJDouFiuNRkMX+ ZNMg== X-Gm-Message-State: AOAM532pmqoaOUttD3xmvFWWKmew1v4V5i4+SgK1inHaNX4zqHrqNiPH gvxcyD+1DrIEDIQESPokaDw= X-Google-Smtp-Source: ABdhPJyB2NgIslUvI/ia3mCeD7m2Ug6Mx0wUq0uOgfqXcYBI1Ik5XQhveJqUc5YZ/iw7PSUC7gF3FQ== X-Received: by 2002:a17:906:934c:: with SMTP id p12mr2032723ejw.131.1617175749973; Wed, 31 Mar 2021 00:29:09 -0700 (PDT) Received: from oberon.vmware.com ([83.222.187.186]) by smtp.gmail.com with ESMTPSA id ho11sm587469ejc.112.2021.03.31.00.29.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Mar 2021 00:29:09 -0700 (PDT) From: "Tzvetomir Stoyanov (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org Subject: [PATCH v34 5/5] trace-cmd: Add KVM timestamp synchronization plugin Date: Wed, 31 Mar 2021 10:29:01 +0300 Message-Id: <20210331072901.152880-6-tz.stoyanov@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210331072901.152880-1-tz.stoyanov@gmail.com> References: <20210331072901.152880-1-tz.stoyanov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Added new timestamp synchronization plugin for KVM hosts. It reads the clock offsets directly from the KVM debug filesystem, if available. The plugin works only with x86-tsc ftrace clock. Note: KVM clock scaling is not supported yet. If a non-default KVM scaling is detected, the KVM plugin is not used for timestamp synchronization. Signed-off-by: Tzvetomir Stoyanov (VMware) --- lib/trace-cmd/Makefile | 1 + lib/trace-cmd/include/trace-tsync-local.h | 1 + lib/trace-cmd/trace-timesync-kvm.c | 533 ++++++++++++++++++++++ lib/trace-cmd/trace-timesync.c | 1 + 4 files changed, 536 insertions(+) create mode 100644 lib/trace-cmd/trace-timesync-kvm.c diff --git a/lib/trace-cmd/Makefile b/lib/trace-cmd/Makefile index 486ea7d1..afd74e1d 100644 --- a/lib/trace-cmd/Makefile +++ b/lib/trace-cmd/Makefile @@ -23,6 +23,7 @@ endif OBJS += trace-timesync.o ifeq ($(VSOCK_DEFINED), 1) OBJS += trace-timesync-ptp.o +OBJS += trace-timesync-kvm.o endif # Additional util objects diff --git a/lib/trace-cmd/include/trace-tsync-local.h b/lib/trace-cmd/include/trace-tsync-local.h index b3a3bdfc..7e56d187 100644 --- a/lib/trace-cmd/include/trace-tsync-local.h +++ b/lib/trace-cmd/include/trace-tsync-local.h @@ -65,5 +65,6 @@ int tracecmd_tsync_proto_register(const char *proto_name, int accuracy, int role int tracecmd_tsync_proto_unregister(char *proto_name); int ptp_clock_sync_register(void); +int kvm_clock_sync_register(void); #endif /* _TRACE_TSYNC_LOCAL_H */ diff --git a/lib/trace-cmd/trace-timesync-kvm.c b/lib/trace-cmd/trace-timesync-kvm.c new file mode 100644 index 00000000..58c028ea --- /dev/null +++ b/lib/trace-cmd/trace-timesync-kvm.c @@ -0,0 +1,533 @@ +// SPDX-License-Identifier: LGPL-2.1 +/* + * Copyright (C) 2020, VMware, Tzvetomir Stoyanov tz.stoyanov@gmail.com> + * + */ + +#include +#include +#include +#include +#include +#include + +#include "trace-cmd.h" +#include "trace-cmd-private.h" +#include "tracefs.h" +#include "trace-tsync-local.h" + +#define KVM_DEBUG_FS "/sys/kernel/debug/kvm" +#define KVM_DEBUG_OFFSET_FILE "tsc-offset" +#define KVM_DEBUG_SCALING_FILE "tsc-scaling-ratio" +#define KVM_DEBUG_VCPU_DIR "vcpu" + +/* default KVM scaling values, taken from the Linux kernel */ +#define KVM_SCALING_AMD_DEFAULT (1ULL<<32) +#define KVM_SCALING_INTEL_DEFAULT (1ULL<<48) + +#define KVM_SYNC_PKT_REQUEST 1 +#define KVM_SYNC_PKT_RESPONSE 2 + +typedef __s64 s64; + +#define KVM_ACCURACY 0 +#define KVM_NAME "kvm" + +struct kvm_clock_sync { + int vcpu_count; + char **vcpu_offsets; + char **vcpu_scalings; + int marker_fd; + struct tep_handle *tep; + int raw_id; + unsigned long long ts; +}; + +struct kvm_clock_offset_msg { + s64 ts; + s64 offset; + s64 scaling; +}; + +static int read_ll_from_file(char *file, long long *res) +{ + char buf[32]; + int ret; + int fd; + + if (!file) + return -1; + fd = open(file, O_RDONLY | O_NONBLOCK); + if (fd < 0) + return -1; + ret = read(fd, buf, 32); + close(fd); + if (ret <= 0) + return -1; + + *res = strtoll(buf, NULL, 0); + + return 0; +} + +static bool kvm_scaling_check_vm_cpu(char *vname, char *cpu) +{ + long long scaling; + char *path; + int ret; + + if (asprintf(&path, "%s/%s/%s", vname, cpu, KVM_DEBUG_SCALING_FILE) < 0) + return true; + ret = read_ll_from_file(path, &scaling); + free(path); + + /* + * If there is a scaling, different from the default - + * return false, not supported. + */ + if (!ret && + scaling != KVM_SCALING_AMD_DEFAULT && scaling != KVM_SCALING_INTEL_DEFAULT) + return false; + + return true; +} + +static bool kvm_scaling_check_vm(char *name) +{ + struct dirent *entry; + char *vdir; + DIR *dir; + + if (asprintf(&vdir, "%s/%s", KVM_DEBUG_FS, name) < 0) + return true; + + dir = opendir(vdir); + if (!dir) { + free(vdir); + return true; + } + while ((entry = readdir(dir))) { + if (entry->d_type == DT_DIR && !strncmp(entry->d_name, "vcpu", 4) && + !kvm_scaling_check_vm_cpu(vdir, entry->d_name)) + break; + } + + closedir(dir); + free(vdir); + return entry == NULL; +} +static bool kvm_scaling_check(void) +{ + struct dirent *entry; + DIR *dir; + + dir = opendir(KVM_DEBUG_FS); + if (!dir) + return true; + + while ((entry = readdir(dir))) { + if (entry->d_type == DT_DIR && isdigit(entry->d_name[0]) && + !kvm_scaling_check_vm(entry->d_name)) + break; + } + closedir(dir); + return entry == NULL; +} + +static bool kvm_support_check(bool guest) +{ + struct stat st; + int ret; + + if (guest) + return true; + + ret = stat(KVM_DEBUG_FS, &st); + if (ret < 0) + return false; + + if (!S_ISDIR(st.st_mode)) + return false; + + return kvm_scaling_check(); +} + +static int kvm_open_vcpu_dir(struct kvm_clock_sync *kvm, int cpu, char *dir_str) +{ + struct dirent *entry; + char path[PATH_MAX]; + DIR *dir; + + dir = opendir(dir_str); + if (!dir) + goto error; + while ((entry = readdir(dir))) { + if (entry->d_type != DT_DIR) { + if (!strncmp(entry->d_name, KVM_DEBUG_OFFSET_FILE, + strlen(KVM_DEBUG_OFFSET_FILE))) { + snprintf(path, sizeof(path), "%s/%s", + dir_str, entry->d_name); + kvm->vcpu_offsets[cpu] = strdup(path); + } + if (!strncmp(entry->d_name, KVM_DEBUG_SCALING_FILE, + strlen(KVM_DEBUG_SCALING_FILE))) { + snprintf(path, sizeof(path), "%s/%s", + dir_str, entry->d_name); + kvm->vcpu_scalings[cpu] = strdup(path); + } + } + } + if (!kvm->vcpu_offsets[cpu]) + goto error; + closedir(dir); + return 0; + +error: + if (dir) + closedir(dir); + free(kvm->vcpu_offsets[cpu]); + kvm->vcpu_offsets[cpu] = NULL; + free(kvm->vcpu_scalings[cpu]); + kvm->vcpu_scalings[cpu] = NULL; + return -1; +} + +static int kvm_open_debug_files(struct kvm_clock_sync *kvm, int pid) +{ + char *vm_dir_str = NULL; + struct dirent *entry; + char *pid_str = NULL; + char path[PATH_MAX]; + long vcpu; + DIR *dir; + int i; + + dir = opendir(KVM_DEBUG_FS); + if (!dir) + goto error; + if (asprintf(&pid_str, "%d-", pid) <= 0) + goto error; + while ((entry = readdir(dir))) { + if (!(entry->d_type == DT_DIR && + !strncmp(entry->d_name, pid_str, strlen(pid_str)))) + continue; + asprintf(&vm_dir_str, "%s/%s", KVM_DEBUG_FS, entry->d_name); + break; + } + closedir(dir); + dir = NULL; + if (!vm_dir_str) + goto error; + dir = opendir(vm_dir_str); + if (!dir) + goto error; + while ((entry = readdir(dir))) { + if (!(entry->d_type == DT_DIR && + !strncmp(entry->d_name, KVM_DEBUG_VCPU_DIR, strlen(KVM_DEBUG_VCPU_DIR)))) + continue; + vcpu = strtol(entry->d_name + strlen(KVM_DEBUG_VCPU_DIR), NULL, 10); + if (vcpu < 0 || vcpu >= kvm->vcpu_count) + continue; + snprintf(path, sizeof(path), "%s/%s", vm_dir_str, entry->d_name); + if (kvm_open_vcpu_dir(kvm, vcpu, path) < 0) + goto error; + } + for (i = 0; i < kvm->vcpu_count; i++) { + if (!kvm->vcpu_offsets[i]) + goto error; + } + closedir(dir); + free(pid_str); + free(vm_dir_str); + return 0; +error: + free(pid_str); + free(vm_dir_str); + if (dir) + closedir(dir); + return -1; +} + +static int kvm_clock_sync_init_host(struct tracecmd_time_sync *tsync, + struct kvm_clock_sync *kvm) +{ + kvm->vcpu_count = tsync->vcpu_count; + kvm->vcpu_offsets = calloc(kvm->vcpu_count, sizeof(char *)); + kvm->vcpu_scalings = calloc(kvm->vcpu_count, sizeof(char *)); + if (!kvm->vcpu_offsets || !kvm->vcpu_scalings) + goto error; + if (kvm_open_debug_files(kvm, tsync->guest_pid) < 0) + goto error; + return 0; + +error: + free(kvm->vcpu_offsets); + free(kvm->vcpu_scalings); + return -1; +} + +static int kvm_clock_sync_init_guest(struct tracecmd_time_sync *tsync, + struct kvm_clock_sync *kvm) +{ + const char *systems[] = {"ftrace", NULL}; + struct clock_sync_context *clock_context; + struct tep_event *raw; + char *path; + + clock_context = (struct clock_sync_context *)tsync->context; + path = tracefs_instance_get_dir(clock_context->instance); + if (!path) + goto error; + kvm->tep = tracefs_local_events_system(path, systems); + tracefs_put_tracing_file(path); + if (!kvm->tep) + goto error; + raw = tep_find_event_by_name(kvm->tep, "ftrace", "raw_data"); + if (!raw) + goto error; + + kvm->raw_id = raw->id; + tep_set_file_bigendian(kvm->tep, tracecmd_host_bigendian()); + tep_set_local_bigendian(kvm->tep, tracecmd_host_bigendian()); + + path = tracefs_instance_get_file(clock_context->instance, "trace_marker_raw"); + if (!path) + goto error; + kvm->marker_fd = open(path, O_WRONLY); + tracefs_put_tracing_file(path); + + return 0; + +error: + if (kvm->tep) + tep_free(kvm->tep); + if (kvm->marker_fd >= 0) + close(kvm->marker_fd); + + return -1; +} + +static int kvm_clock_sync_init(struct tracecmd_time_sync *tsync) +{ + struct clock_sync_context *clock_context; + struct kvm_clock_sync *kvm; + int ret; + + if (!tsync || !tsync->context) + return -1; + clock_context = (struct clock_sync_context *)tsync->context; + + if (!kvm_support_check(clock_context->is_guest)) + return -1; + kvm = calloc(1, sizeof(struct kvm_clock_sync)); + if (!kvm) + return -1; + kvm->marker_fd = -1; + if (clock_context->is_guest) + ret = kvm_clock_sync_init_guest(tsync, kvm); + else + ret = kvm_clock_sync_init_host(tsync, kvm); + if (ret < 0) + goto error; + + clock_context->proto_data = kvm; + return 0; + +error: + free(kvm); + return -1; +} + +static int kvm_clock_sync_free(struct tracecmd_time_sync *tsync) +{ + struct clock_sync_context *clock_context; + struct kvm_clock_sync *kvm = NULL; + int i; + + clock_context = (struct clock_sync_context *)tsync->context; + if (clock_context) + kvm = (struct kvm_clock_sync *)clock_context->proto_data; + if (kvm) { + for (i = 0; i < kvm->vcpu_count; i++) { + free(kvm->vcpu_offsets[i]); + kvm->vcpu_offsets[i] = NULL; + free(kvm->vcpu_scalings[i]); + kvm->vcpu_scalings[i] = NULL; + } + if (kvm->tep) + tep_free(kvm->tep); + if (kvm->marker_fd >= 0) + close(kvm->marker_fd); + free(kvm); + } + return -1; +} + +static int kvm_clock_host(struct tracecmd_time_sync *tsync, + long long *offset, long long *scaling, + long long *timestamp, unsigned int cpu) +{ + char sync_proto[TRACECMD_TSYNC_PNAME_LENGTH]; + struct clock_sync_context *clock_context; + struct kvm_clock_offset_msg packet; + struct kvm_clock_sync *kvm = NULL; + long long kvm_scaling = 1; + unsigned int sync_msg; + long long kvm_offset; + unsigned int size; + char *msg; + int ret; + + clock_context = (struct clock_sync_context *)tsync->context; + if (clock_context) + kvm = (struct kvm_clock_sync *)clock_context->proto_data; + if (!kvm || !kvm->vcpu_offsets || !kvm->vcpu_offsets[0]) + return -1; + if (cpu >= kvm->vcpu_count) + return -1; + ret = read_ll_from_file(kvm->vcpu_offsets[cpu], &kvm_offset); + if (ret < 0) + return -1; + if (kvm->vcpu_scalings && kvm->vcpu_scalings[cpu]) { + read_ll_from_file(kvm->vcpu_scalings[cpu], &kvm_scaling); + if (kvm_scaling == KVM_SCALING_AMD_DEFAULT || + kvm_scaling == KVM_SCALING_INTEL_DEFAULT) + kvm_scaling = 1; + } + msg = (char *)&packet; + size = sizeof(packet); + ret = tracecmd_msg_recv_time_sync(tsync->msg_handle, + sync_proto, &sync_msg, + &size, &msg); + if (ret || strncmp(sync_proto, KVM_NAME, TRACECMD_TSYNC_PNAME_LENGTH) || + sync_msg != KVM_SYNC_PKT_REQUEST) + return -1; + + packet.offset = -kvm_offset; + packet.scaling = kvm_scaling; + ret = tracecmd_msg_send_time_sync(tsync->msg_handle, KVM_NAME, + KVM_SYNC_PKT_RESPONSE, sizeof(packet), + (char *)&packet); + if (ret) + return -1; + + *scaling = packet.scaling; + *offset = packet.offset; + *timestamp = packet.ts; + + return 0; +} + +#define KVM_EVENT_MARKER "kvm sync event" +static int kvm_marker_find(struct tep_event *event, struct tep_record *record, + int cpu, void *context) +{ + struct kvm_clock_sync *kvm = (struct kvm_clock_sync *)context; + struct tep_format_field *field; + struct tep_format_field *id; + char *marker; + + /* Make sure this is our event */ + if (event->id != kvm->raw_id) + return 0; + id = tep_find_field(event, "id"); + field = tep_find_field(event, "buf"); + if (field && id && + record->size >= (id->offset + strlen(KVM_EVENT_MARKER) + 1)) { + marker = (char *)(record->data + id->offset); + if (!strcmp(marker, KVM_EVENT_MARKER)) { + kvm->ts = record->ts; + return 1; + } + } + + return 0; +} + + +static int kvm_clock_guest(struct tracecmd_time_sync *tsync, + long long *offset, + long long *scaling, + long long *timestamp) +{ + char sync_proto[TRACECMD_TSYNC_PNAME_LENGTH]; + struct clock_sync_context *clock_context; + struct kvm_clock_offset_msg packet; + struct kvm_clock_sync *kvm = NULL; + unsigned int sync_msg; + unsigned int size; + char *msg; + int ret; + + clock_context = (struct clock_sync_context *)tsync->context; + if (clock_context) + kvm = (struct kvm_clock_sync *)clock_context->proto_data; + if (!kvm) + return -1; + kvm->ts = 0; + memset(&packet, 0, sizeof(packet)); + tracefs_instance_file_write(clock_context->instance, "trace", "\0"); + write(kvm->marker_fd, KVM_EVENT_MARKER, strlen(KVM_EVENT_MARKER) + 1); + kvm->ts = 0; + tracefs_iterate_raw_events(kvm->tep, clock_context->instance, + NULL, 0, kvm_marker_find, kvm); + packet.ts = kvm->ts; + ret = tracecmd_msg_send_time_sync(tsync->msg_handle, KVM_NAME, + KVM_SYNC_PKT_REQUEST, sizeof(packet), + (char *)&packet); + if (ret) + return -1; + msg = (char *)&packet; + size = sizeof(packet); + ret = tracecmd_msg_recv_time_sync(tsync->msg_handle, + sync_proto, &sync_msg, + &size, &msg); + if (ret || strncmp(sync_proto, KVM_NAME, TRACECMD_TSYNC_PNAME_LENGTH) || + sync_msg != KVM_SYNC_PKT_RESPONSE) + return -1; + + *scaling = packet.scaling; + *offset = packet.offset; + *timestamp = packet.ts; + return 0; +} + +static int kvm_clock_sync_calc(struct tracecmd_time_sync *tsync, + long long *offset, long long *scaling, + long long *timestamp, unsigned int cpu) +{ + struct clock_sync_context *clock_context; + int ret; + + if (!tsync || !tsync->context) + return -1; + + clock_context = (struct clock_sync_context *)tsync->context; + + if (clock_context->is_guest) + ret = kvm_clock_guest(tsync, offset, scaling, timestamp); + else + ret = kvm_clock_host(tsync, offset, scaling, timestamp, cpu); + return ret; +} + +int kvm_clock_sync_register(void) +{ + int role = TRACECMD_TIME_SYNC_ROLE_GUEST; + int clock = 0; + + if (kvm_support_check(false)) { + role |= TRACECMD_TIME_SYNC_ROLE_HOST; + clock = TRACECMD_CLOCK_X86_TSC; + } + return tracecmd_tsync_proto_register(KVM_NAME, KVM_ACCURACY, + role, clock, 0, + kvm_clock_sync_init, + kvm_clock_sync_free, + kvm_clock_sync_calc); +} + +int kvm_clock_sync_unregister(void) +{ + return tracecmd_tsync_proto_unregister(KVM_NAME); +} diff --git a/lib/trace-cmd/trace-timesync.c b/lib/trace-cmd/trace-timesync.c index 7d275019..86d77810 100644 --- a/lib/trace-cmd/trace-timesync.c +++ b/lib/trace-cmd/trace-timesync.c @@ -66,6 +66,7 @@ void tracecmd_tsync_init(void) { #ifdef VSOCK ptp_clock_sync_register(); + kvm_clock_sync_register(); #endif }