On Tue, Dec 03, 2024 at 05:33:04PM +0000, David Woodhouse wrote:
> From: David Woodhouse <d...@amazon.co.uk>
>
> The vmclock device addresses the problem of live migration with
> precision clocks. The tolerances of a hardware counter (e.g. TSC) are
> typically around ±50PPM. A guest will use NTP/PTP/PPS to discipline that
> counter against an external source of 'real' time, and track the precise
> frequency of the counter as it changes with environmental conditions.
>
> When a guest is live migrated, anything it knows about the frequency of
> the underlying counter becomes invalid. It may move from a host where
> the counter running at -50PPM of its nominal frequency, to a host where
> it runs at +50PPM. There will also be a step change in the value of the
> counter, as the correctness of its absolute value at migration is
> limited by the accuracy of the source and destination host's time
> synchronization.
>
> The device exposes a shared memory region to guests, which can be mapped
> all the way to userspace. In the first phase, this merely advertises a
> 'disruption_marker', which indicates that the guest should throw away any
> NTP synchronization it thinks it has, and start again.
>
> Because the region can be exposed all the way to userspace, applications
> can still use time from a fast vDSO 'system call', and check the
> disruption marker to be sure that their timestamp is indeed truthful.
>
> The structure also allows for the precise time, as known by the host, to
> be exposed directly to guests so that they don't have to wait for NTP to
> resync from scratch.
>
> The values and fields are based on the nascent virtio-rtc specification,
> and the intent is that a version (hopefully precisely this version) of
> this structure will be included as an optional part of that spec. In the
> meantime, a simple ACPI device along the lines of VMGENID is perfectly
> sufficient and is compatible with what's being shipped in certain
> commercial hypervisors.
>
> Linux guest support was merged into the 6.13-rc1 kernel:
> https://git.kernel.org/torvalds/c/205032724226
>
> Signed-off-by: David Woodhouse <d...@amazon.co.uk>
It's tagged, will be in the next pull. Thanks!
> ---
> This is basically unchanged since the last time the structure was
> changed in July, apart from fairly trivial cosmetic changes and now
> importing the header file from Linux.
>
>
> v5:
> • Trivial simplification to AML generation.
> • Import vmclock-abi.h from Linux now the guest support is merged.
>
> v4:
> • Trivial checkpatch fixes and comment improvements.
>
> v3:
> • Add comment that vmclock-abi.h will come from the Linux kernel
> headers once it gets merged there.
>
> v2:
> • Change esterror/maxerror fields to nanoseconds.
> • Change to officially assigned AMZNC10C ACPI HID.
> • Fix little-endian handling of fields in update.
>
> hw/acpi/Kconfig | 5 +
> hw/acpi/meson.build | 1 +
> hw/acpi/vmclock.c | 184 +++++++++++++++++++
> hw/i386/Kconfig | 1 +
> hw/i386/acpi-build.c | 10 +-
> include/hw/acpi/vmclock.h | 34 ++++
> include/standard-headers/linux/vmclock-abi.h | 182 ++++++++++++++++++
> scripts/update-linux-headers.sh | 1 +
> 8 files changed, 417 insertions(+), 1 deletion(-)
> create mode 100644 hw/acpi/vmclock.c
> create mode 100644 include/hw/acpi/vmclock.h
> create mode 100644 include/standard-headers/linux/vmclock-abi.h
>
> diff --git a/hw/acpi/Kconfig b/hw/acpi/Kconfig
> index e07d3204eb..1d4e9f0845 100644
> --- a/hw/acpi/Kconfig
> +++ b/hw/acpi/Kconfig
> @@ -60,6 +60,11 @@ config ACPI_VMGENID
> default y
> depends on PC
>
> +config ACPI_VMCLOCK
> + bool
> + default y
> + depends on PC
> +
> config ACPI_VIOT
> bool
> depends on ACPI
> diff --git a/hw/acpi/meson.build b/hw/acpi/meson.build
> index c8854f4d48..73f02b9691 100644
> --- a/hw/acpi/meson.build
> +++ b/hw/acpi/meson.build
> @@ -15,6 +15,7 @@ acpi_ss.add(when: 'CONFIG_ACPI_NVDIMM', if_false:
> files('acpi-nvdimm-stub.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_PCI', if_true: files('pci.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_CXL', if_true: files('cxl.c'), if_false:
> files('cxl-stub.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_VMGENID', if_true: files('vmgenid.c'))
> +acpi_ss.add(when: 'CONFIG_ACPI_VMCLOCK', if_true: files('vmclock.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_HW_REDUCED', if_true:
> files('generic_event_device.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_HMAT', if_true: files('hmat.c'))
> acpi_ss.add(when: 'CONFIG_ACPI_APEI', if_true: files('ghes.c'), if_false:
> files('ghes-stub.c'))
> diff --git a/hw/acpi/vmclock.c b/hw/acpi/vmclock.c
> new file mode 100644
> index 0000000000..541c06c22b
> --- /dev/null
> +++ b/hw/acpi/vmclock.c
> @@ -0,0 +1,184 @@
> +/*
> + * Virtual Machine Clock Device
> + *
> + * Copyright © 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
> + *
> + * Authors: David Woodhouse <dw...@infradead.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qemu/module.h"
> +#include "hw/i386/e820_memory_layout.h"
> +#include "hw/acpi/acpi.h"
> +#include "hw/acpi/aml-build.h"
> +#include "hw/acpi/vmclock.h"
> +#include "hw/nvram/fw_cfg.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/qdev-properties-system.h"
> +#include "migration/vmstate.h"
> +#include "sysemu/reset.h"
> +
> +#include "standard-headers/linux/vmclock-abi.h"
> +
> +void vmclock_build_acpi(VmclockState *vms, GArray *table_data,
> + BIOSLinker *linker, const char *oem_id)
> +{
> + Aml *ssdt, *dev, *scope, *crs;
> + AcpiTable table = { .sig = "SSDT", .rev = 1,
> + .oem_id = oem_id, .oem_table_id = "VMCLOCK" };
> +
> + /* Put VMCLOCK into a separate SSDT table */
> + acpi_table_begin(&table, table_data);
> + ssdt = init_aml_allocator();
> +
> + scope = aml_scope("\\_SB");
> + dev = aml_device("VCLK");
> + aml_append(dev, aml_name_decl("_HID", aml_string("AMZNC10C")));
> + aml_append(dev, aml_name_decl("_CID", aml_string("VMCLOCK")));
> + aml_append(dev, aml_name_decl("_DDN", aml_string("VMCLOCK")));
> +
> + /* Simple status method */
> + aml_append(dev, aml_name_decl("_STA", aml_int(0xf)));
> +
> + crs = aml_resource_template();
> + aml_append(crs, aml_qword_memory(AML_POS_DECODE,
> + AML_MIN_FIXED, AML_MAX_FIXED,
> + AML_CACHEABLE, AML_READ_ONLY,
> + 0xffffffffffffffffULL,
> + vms->physaddr,
> + vms->physaddr + VMCLOCK_SIZE - 1,
> + 0, VMCLOCK_SIZE));
> + aml_append(dev, aml_name_decl("_CRS", crs));
> + aml_append(scope, dev);
> + aml_append(ssdt, scope);
> +
> + g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
> + acpi_table_end(linker, &table);
> + free_aml_allocator();
> +}
> +
> +static void vmclock_update_guest(VmclockState *vms)
> +{
> + uint64_t disruption_marker;
> + uint32_t seq_count;
> +
> + if (!vms->clk) {
> + return;
> + }
> +
> + seq_count = le32_to_cpu(vms->clk->seq_count) | 1;
> + vms->clk->seq_count = cpu_to_le32(seq_count);
> + /* These barriers pair with read barriers in the guest */
> + smp_wmb();
> +
> + disruption_marker = le64_to_cpu(vms->clk->disruption_marker);
> + disruption_marker++;
> + vms->clk->disruption_marker = cpu_to_le64(disruption_marker);
> +
> + /* These barriers pair with read barriers in the guest */
> + smp_wmb();
> + vms->clk->seq_count = cpu_to_le32(seq_count + 1);
> +}
> +
> +/*
> + * After restoring an image, we need to update the guest memory to notify
> + * it of clock disruption.
> + */
> +static int vmclock_post_load(void *opaque, int version_id)
> +{
> + VmclockState *vms = opaque;
> +
> + vmclock_update_guest(vms);
> + return 0;
> +}
> +
> +static const VMStateDescription vmstate_vmclock = {
> + .name = "vmclock",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .post_load = vmclock_post_load,
> + .fields = (const VMStateField[]) {
> + VMSTATE_UINT64(physaddr, VmclockState),
> + VMSTATE_END_OF_LIST()
> + },
> +};
> +
> +static void vmclock_handle_reset(void *opaque)
> +{
> + VmclockState *vms = VMCLOCK(opaque);
> +
> + if (!memory_region_is_mapped(&vms->clk_page)) {
> + memory_region_add_subregion_overlap(get_system_memory(),
> + vms->physaddr,
> + &vms->clk_page, 0);
> + }
> +}
> +
> +static void vmclock_realize(DeviceState *dev, Error **errp)
> +{
> + VmclockState *vms = VMCLOCK(dev);
> +
> + /*
> + * Given that this function is executing, there is at least one VMCLOCK
> + * device. Check if there are several.
> + */
> + if (!find_vmclock_dev()) {
> + error_setg(errp, "at most one %s device is permitted", TYPE_VMCLOCK);
> + return;
> + }
> +
> + vms->physaddr = VMCLOCK_ADDR;
> +
> + e820_add_entry(vms->physaddr, VMCLOCK_SIZE, E820_RESERVED);
> +
> + memory_region_init_ram(&vms->clk_page, OBJECT(dev), "vmclock_page",
> + VMCLOCK_SIZE, &error_abort);
> + memory_region_set_enabled(&vms->clk_page, true);
> + vms->clk = memory_region_get_ram_ptr(&vms->clk_page);
> + memset(vms->clk, 0, VMCLOCK_SIZE);
> +
> + vms->clk->magic = cpu_to_le32(VMCLOCK_MAGIC);
> + vms->clk->size = cpu_to_le16(VMCLOCK_SIZE);
> + vms->clk->version = cpu_to_le16(1);
> +
> + /* These are all zero and thus default, but be explicit */
> + vms->clk->clock_status = VMCLOCK_STATUS_UNKNOWN;
> + vms->clk->counter_id = VMCLOCK_COUNTER_INVALID;
> +
> + qemu_register_reset(vmclock_handle_reset, vms);
> +
> + vmclock_update_guest(vms);
> +}
> +
> +static Property vmclock_device_properties[] = {
> + DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void vmclock_device_class_init(ObjectClass *klass, void *data)
> +{
> + DeviceClass *dc = DEVICE_CLASS(klass);
> +
> + dc->vmsd = &vmstate_vmclock;
> + dc->realize = vmclock_realize;
> + device_class_set_props(dc, vmclock_device_properties);
> + dc->hotpluggable = false;
> + set_bit(DEVICE_CATEGORY_MISC, dc->categories);
> +}
> +
> +static const TypeInfo vmclock_device_info = {
> + .name = TYPE_VMCLOCK,
> + .parent = TYPE_DEVICE,
> + .instance_size = sizeof(VmclockState),
> + .class_init = vmclock_device_class_init,
> +};
> +
> +static void vmclock_register_types(void)
> +{
> + type_register_static(&vmclock_device_info);
> +}
> +
> +type_init(vmclock_register_types)
> diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
> index 32818480d2..d34ce07b21 100644
> --- a/hw/i386/Kconfig
> +++ b/hw/i386/Kconfig
> @@ -43,6 +43,7 @@ config PC
> select SERIAL_ISA
> select ACPI_PCI
> select ACPI_VMGENID
> + select ACPI_VMCLOCK
> select VIRTIO_PMEM_SUPPORTED
> select VIRTIO_MEM_SUPPORTED
> select HV_BALLOON_SUPPORTED
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 9fcc2897b8..941af69ed3 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -43,6 +43,7 @@
> #include "sysemu/tpm.h"
> #include "hw/acpi/tpm.h"
> #include "hw/acpi/vmgenid.h"
> +#include "hw/acpi/vmclock.h"
> #include "hw/acpi/erst.h"
> #include "hw/acpi/piix4.h"
> #include "sysemu/tpm_backend.h"
> @@ -2432,7 +2433,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState
> *machine)
> uint8_t *u;
> GArray *tables_blob = tables->table_data;
> AcpiSlicOem slic_oem = { .id = NULL, .table_id = NULL };
> - Object *vmgenid_dev;
> + Object *vmgenid_dev, *vmclock_dev;
> char *oem_id;
> char *oem_table_id;
>
> @@ -2505,6 +2506,13 @@ void acpi_build(AcpiBuildTables *tables, MachineState
> *machine)
> tables->vmgenid, tables->linker, x86ms->oem_id);
> }
>
> + vmclock_dev = find_vmclock_dev();
> + if (vmclock_dev) {
> + acpi_add_table(table_offsets, tables_blob);
> + vmclock_build_acpi(VMCLOCK(vmclock_dev), tables_blob, tables->linker,
> + x86ms->oem_id);
> + }
> +
> if (misc.has_hpet) {
> acpi_add_table(table_offsets, tables_blob);
> build_hpet(tables_blob, tables->linker, x86ms->oem_id,
> diff --git a/include/hw/acpi/vmclock.h b/include/hw/acpi/vmclock.h
> new file mode 100644
> index 0000000000..5605605812
> --- /dev/null
> +++ b/include/hw/acpi/vmclock.h
> @@ -0,0 +1,34 @@
> +#ifndef ACPI_VMCLOCK_H
> +#define ACPI_VMCLOCK_H
> +
> +#include "hw/acpi/bios-linker-loader.h"
> +#include "hw/qdev-core.h"
> +#include "qemu/uuid.h"
> +#include "qom/object.h"
> +
> +#define TYPE_VMCLOCK "vmclock"
> +
> +#define VMCLOCK_ADDR 0xfeffb000
> +#define VMCLOCK_SIZE 0x1000
> +
> +OBJECT_DECLARE_SIMPLE_TYPE(VmclockState, VMCLOCK)
> +
> +struct vmclock_abi;
> +
> +struct VmclockState {
> + DeviceState parent_obj;
> + MemoryRegion clk_page;
> + uint64_t physaddr;
> + struct vmclock_abi *clk;
> +};
> +
> +/* returns NULL unless there is exactly one device */
> +static inline Object *find_vmclock_dev(void)
> +{
> + return object_resolve_path_type("", TYPE_VMCLOCK, NULL);
> +}
> +
> +void vmclock_build_acpi(VmclockState *vms, GArray *table_data,
> + BIOSLinker *linker, const char *oem_id);
> +
> +#endif
> diff --git a/include/standard-headers/linux/vmclock-abi.h
> b/include/standard-headers/linux/vmclock-abi.h
> new file mode 100644
> index 0000000000..15b0316cb4
> --- /dev/null
> +++ b/include/standard-headers/linux/vmclock-abi.h
> @@ -0,0 +1,182 @@
> +/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR
> BSD-2-Clause) */
> +
> +/*
> + * This structure provides a vDSO-style clock to VM guests, exposing the
> + * relationship (or lack thereof) between the CPU clock (TSC, timebase, arch
> + * counter, etc.) and real time. It is designed to address the problem of
> + * live migration, which other clock enlightenments do not.
> + *
> + * When a guest is live migrated, this affects the clock in two ways.
> + *
> + * First, even between identical hosts the actual frequency of the underlying
> + * counter will change within the tolerances of its specification (typically
> + * ±50PPM, or 4 seconds a day). This frequency also varies over time on the
> + * same host, but can be tracked by NTP as it generally varies slowly. With
> + * live migration there is a step change in the frequency, with no warning.
> + *
> + * Second, there may be a step change in the value of the counter itself, as
> + * its accuracy is limited by the precision of the NTP synchronization on the
> + * source and destination hosts.
> + *
> + * So any calibration (NTP, PTP, etc.) which the guest has done on the source
> + * host before migration is invalid, and needs to be redone on the new host.
> + *
> + * In its most basic mode, this structure provides only an indication to the
> + * guest that live migration has occurred. This allows the guest to know that
> + * its clock is invalid and take remedial action. For applications that need
> + * reliable accurate timestamps (e.g. distributed databases), the structure
> + * can be mapped all the way to userspace. This allows the application to see
> + * directly for itself that the clock is disrupted and take appropriate
> + * action, even when using a vDSO-style method to get the time instead of a
> + * system call.
> + *
> + * In its more advanced mode. this structure can also be used to expose the
> + * precise relationship of the CPU counter to real time, as calibrated by the
> + * host. This means that userspace applications can have accurate time
> + * immediately after live migration, rather than having to pause operations
> + * and wait for NTP to recover. This mode does, of course, rely on the
> + * counter being reliable and consistent across CPUs.
> + *
> + * Note that this must be true UTC, never with smeared leap seconds. If a
> + * guest wishes to construct a smeared clock, it can do so. Presenting a
> + * smeared clock through this interface would be problematic because it
> + * actually messes with the apparent counter *period*. A linear smearing
> + * of 1 ms per second would effectively tweak the counter period by 1000PPM
> + * at the start/end of the smearing period, while a sinusoidal smear would
> + * basically be impossible to represent.
> + *
> + * This structure is offered with the intent that it be adopted into the
> + * nascent virtio-rtc standard, as a virtio-rtc that does not address the
> live
> + * migration problem seems a little less than fit for purpose. For that
> + * reason, certain fields use precisely the same numeric definitions as in
> + * the virtio-rtc proposal. The structure can also be exposed through an ACPI
> + * device with the CID "VMCLOCK", modelled on the "VMGENID" device except for
> + * the fact that it uses a real _CRS to convey the address of the structure
> + * (which should be a full page, to allow for mapping directly to userspace).
> + */
> +
> +#ifndef __VMCLOCK_ABI_H__
> +#define __VMCLOCK_ABI_H__
> +
> +#include "standard-headers/linux/types.h"
> +
> +struct vmclock_abi {
> + /* CONSTANT FIELDS */
> + uint32_t magic;
> +#define VMCLOCK_MAGIC 0x4b4c4356 /* "VCLK" */
> + uint32_t size; /* Size of region containing this structure */
> + uint16_t version; /* 1 */
> + uint8_t counter_id; /* Matches VIRTIO_RTC_COUNTER_xxx except INVALID */
> +#define VMCLOCK_COUNTER_ARM_VCNT 0
> +#define VMCLOCK_COUNTER_X86_TSC 1
> +#define VMCLOCK_COUNTER_INVALID 0xff
> + uint8_t time_type; /* Matches VIRTIO_RTC_TYPE_xxx */
> +#define VMCLOCK_TIME_UTC 0 /* Since 1970-01-01
> 00:00:00z */
> +#define VMCLOCK_TIME_TAI 1 /* Since 1970-01-01
> 00:00:00z */
> +#define VMCLOCK_TIME_MONOTONIC 2 /* Since
> undefined epoch */
> +#define VMCLOCK_TIME_INVALID_SMEARED 3 /* Not supported */
> +#define VMCLOCK_TIME_INVALID_MAYBE_SMEARED 4 /* Not supported */
> +
> + /* NON-CONSTANT FIELDS PROTECTED BY SEQCOUNT LOCK */
> + uint32_t seq_count; /* Low bit means an update is in progress */
> + /*
> + * This field changes to another non-repeating value when the CPU
> + * counter is disrupted, for example on live migration. This lets
> + * the guest know that it should discard any calibration it has
> + * performed of the counter against external sources (NTP/PTP/etc.).
> + */
> + uint64_t disruption_marker;
> + uint64_t flags;
> + /* Indicates that the tai_offset_sec field is valid */
> +#define VMCLOCK_FLAG_TAI_OFFSET_VALID (1 << 0)
> + /*
> + * Optionally used to notify guests of pending maintenance events.
> + * A guest which provides latency-sensitive services may wish to
> + * remove itself from service if an event is coming up. Two flags
> + * indicate the approximate imminence of the event.
> + */
> +#define VMCLOCK_FLAG_DISRUPTION_SOON (1 << 1) /* About a day */
> +#define VMCLOCK_FLAG_DISRUPTION_IMMINENT (1 << 2) /* About an hour */
> +#define VMCLOCK_FLAG_PERIOD_ESTERROR_VALID (1 << 3)
> +#define VMCLOCK_FLAG_PERIOD_MAXERROR_VALID (1 << 4)
> +#define VMCLOCK_FLAG_TIME_ESTERROR_VALID (1 << 5)
> +#define VMCLOCK_FLAG_TIME_MAXERROR_VALID (1 << 6)
> + /*
> + * If the MONOTONIC flag is set then (other than leap seconds) it is
> + * guaranteed that the time calculated according this structure at
> + * any given moment shall never appear to be later than the time
> + * calculated via the structure at any *later* moment.
> + *
> + * In particular, a timestamp based on a counter reading taken
> + * immediately after setting the low bit of seq_count (and the
> + * associated memory barrier), using the previously-valid time and
> + * period fields, shall never be later than a timestamp based on
> + * a counter reading taken immediately before *clearing* the low
> + * bit again after the update, using the about-to-be-valid fields.
> + */
> +#define VMCLOCK_FLAG_TIME_MONOTONIC (1 << 7)
> +
> + uint8_t pad[2];
> + uint8_t clock_status;
> +#define VMCLOCK_STATUS_UNKNOWN 0
> +#define VMCLOCK_STATUS_INITIALIZING 1
> +#define VMCLOCK_STATUS_SYNCHRONIZED 2
> +#define VMCLOCK_STATUS_FREERUNNING 3
> +#define VMCLOCK_STATUS_UNRELIABLE 4
> +
> + /*
> + * The time exposed through this device is never smeared. This field
> + * corresponds to the 'subtype' field in virtio-rtc, which indicates
> + * the smearing method. However in this case it provides a *hint* to
> + * the guest operating system, such that *if* the guest OS wants to
> + * provide its users with an alternative clock which does not follow
> + * UTC, it may do so in a fashion consistent with the other systems
> + * in the nearby environment.
> + */
> + uint8_t leap_second_smearing_hint; /* Matches VIRTIO_RTC_SUBTYPE_xxx */
> +#define VMCLOCK_SMEARING_STRICT 0
> +#define VMCLOCK_SMEARING_NOON_LINEAR 1
> +#define VMCLOCK_SMEARING_UTC_SLS 2
> + uint16_t tai_offset_sec; /* Actually two's complement signed */
> + uint8_t leap_indicator;
> + /*
> + * This field is based on the VIRTIO_RTC_LEAP_xxx values as defined
> + * in the current draft of virtio-rtc, but since smearing cannot be
> + * used with the shared memory device, some values are not used.
> + *
> + * The _POST_POS and _POST_NEG values allow the guest to perform
> + * its own smearing during the day or so after a leap second when
> + * such smearing may need to continue being applied for a leap
> + * second which is now theoretically "historical".
> + */
> +#define VMCLOCK_LEAP_NONE 0x00 /* No known nearby leap second */
> +#define VMCLOCK_LEAP_PRE_POS 0x01 /* Positive leap second at EOM */
> +#define VMCLOCK_LEAP_PRE_NEG 0x02 /* Negative leap second at EOM */
> +#define VMCLOCK_LEAP_POS 0x03 /* Set during 23:59:60 second */
> +#define VMCLOCK_LEAP_POST_POS 0x04
> +#define VMCLOCK_LEAP_POST_NEG 0x05
> +
> + /* Bit shift for counter_period_frac_sec and its error rate */
> + uint8_t counter_period_shift;
> + /*
> + * Paired values of counter and UTC at a given point in time.
> + */
> + uint64_t counter_value;
> + /*
> + * Counter period, and error margin of same. The unit of these
> + * fields is 1/2^(64 + counter_period_shift) of a second.
> + */
> + uint64_t counter_period_frac_sec;
> + uint64_t counter_period_esterror_rate_frac_sec;
> + uint64_t counter_period_maxerror_rate_frac_sec;
> +
> + /*
> + * Time according to time_type field above.
> + */
> + uint64_t time_sec; /* Seconds since time_type epoch */
> + uint64_t time_frac_sec; /* Units of 1/2^64 of a second */
> + uint64_t time_esterror_nanosec;
> + uint64_t time_maxerror_nanosec;
> +};
> +
> +#endif /* __VMCLOCK_ABI_H__ */
> diff --git a/scripts/update-linux-headers.sh b/scripts/update-linux-headers.sh
> index 99a8d9fa4c..8913e4fb99 100755
> --- a/scripts/update-linux-headers.sh
> +++ b/scripts/update-linux-headers.sh
> @@ -258,6 +258,7 @@ for i in "$hdrdir"/include/linux/*virtio*.h \
> "$hdrdir/include/linux/kernel.h" \
> "$hdrdir/include/linux/kvm_para.h" \
> "$hdrdir/include/linux/vhost_types.h" \
> + "$hdrdir/include/linux/vmclock-abi.h" \
> "$hdrdir/include/linux/sysinfo.h"; do
> cp_portable "$i" "$output/include/standard-headers/linux"
> done
> --
> 2.47.0
>
>
