mirror of
https://github.com/Motorhead1991/qemu.git
synced 2025-07-27 04:13:53 -06:00
3634039b93
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 <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org> Message-Id: <07fd5e2f529098ad4d7cab1423fe9f4a03a9cc14.camel@infradead.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
85 lines
1.2 KiB
Text
85 lines
1.2 KiB
Text
config ACPI
|
|
bool
|
|
|
|
config ACPI_X86
|
|
bool
|
|
select ACPI
|
|
select ACPI_NVDIMM
|
|
select ACPI_CXL
|
|
select ACPI_CPU_HOTPLUG
|
|
select ACPI_MEMORY_HOTPLUG
|
|
select ACPI_HMAT
|
|
select ACPI_PCIHP
|
|
select ACPI_ERST
|
|
|
|
config ACPI_ICH9
|
|
bool
|
|
select ACPI_SMBUS
|
|
select ACPI_X86
|
|
select APM
|
|
|
|
config ACPI_CPU_HOTPLUG
|
|
bool
|
|
|
|
config ACPI_MEMORY_HOTPLUG
|
|
bool
|
|
select MEM_DEVICE
|
|
|
|
config ACPI_NVDIMM
|
|
bool
|
|
depends on ACPI
|
|
|
|
config ACPI_PIIX4
|
|
bool
|
|
select ACPI
|
|
select ACPI_SMBUS
|
|
select APM
|
|
|
|
config ACPI_PCIHP
|
|
bool
|
|
depends on ACPI
|
|
|
|
config ACPI_PCI_BRIDGE
|
|
bool
|
|
depends on ACPI && PCI && ACPI_PCIHP
|
|
|
|
config ACPI_HMAT
|
|
bool
|
|
depends on ACPI
|
|
|
|
config ACPI_APEI
|
|
bool
|
|
depends on ACPI
|
|
|
|
config ACPI_PCI
|
|
bool
|
|
depends on ACPI && PCI
|
|
|
|
config ACPI_VMGENID
|
|
bool
|
|
default y
|
|
depends on PC
|
|
|
|
config ACPI_VMCLOCK
|
|
bool
|
|
default y
|
|
depends on PC
|
|
|
|
config ACPI_VIOT
|
|
bool
|
|
depends on ACPI
|
|
|
|
config ACPI_HW_REDUCED
|
|
bool
|
|
select ACPI
|
|
select ACPI_MEMORY_HOTPLUG
|
|
select ACPI_NVDIMM
|
|
|
|
config ACPI_ERST
|
|
bool
|
|
default y
|
|
depends on ACPI && PCI
|
|
|
|
config ACPI_CXL
|
|
bool
|
|
depends on ACPI
|