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Expose the virtio-rtc UTC-like clock as an RTC clock to userspace - if it is present, and if it does not step on leap seconds. The RTC class enables the virtio-rtc device to resume the system from sleep states on RTC alarm. Support RTC alarm if the virtio-rtc alarm feature is present. The virtio-rtc device signals an alarm by marking an alarmq buffer as used. Peculiarities ------------- A virtio-rtc clock is a bit special for an RTC clock in that - the clock may step (also backwards) autonomously at any time and - the device, and its notification mechanism, will be reset during boot or resume from sleep. The virtio-rtc device avoids that the driver might miss an alarm. The device signals an alarm whenever the clock has reached or passed the alarm time, and also when the device is reset (on boot or resume from sleep), if the alarm time is in the past. Open Issue ---------- The CLOCK_BOOTTIME_ALARM will use the RTC clock to wake up from sleep, and implicitly assumes that no RTC clock steps will occur during sleep. The RTC class driver does not know whether the current alarm is a real-time alarm or a boot-time alarm. Perhaps this might be handled by the driver also setting a virtio-rtc monotonic alarm (which uses a clock similar to CLOCK_BOOTTIME_ALARM). The virtio-rtc monotonic alarm would just be used to wake up in case it was a CLOCK_BOOTTIME_ALARM alarm. Otherwise, the behavior should not differ from other RTC class drivers. Signed-off-by: Peter Hilber <quic_philber@quicinc.com> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Message-Id: <20250509160734.1772-5-quic_philber@quicinc.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
255 lines
7.4 KiB
Text
255 lines
7.4 KiB
Text
# SPDX-License-Identifier: GPL-2.0-only
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config VIRTIO_ANCHOR
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bool
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config VIRTIO
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tristate
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select VIRTIO_ANCHOR
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help
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This option is selected by any driver which implements the virtio
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bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
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or CONFIG_S390_GUEST.
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config VIRTIO_PCI_LIB
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tristate
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help
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Modern PCI device implementation. This module implements the
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basic probe and control for devices which are based on modern
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PCI device with possible vendor specific extensions. Any
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module that selects this module must depend on PCI.
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config VIRTIO_PCI_LIB_LEGACY
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tristate
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help
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Legacy PCI device (Virtio PCI Card 0.9.x Draft and older device)
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implementation.
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This module implements the basic probe and control for devices
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which are based on legacy PCI device. Any module that selects this
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module must depend on PCI.
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menuconfig VIRTIO_MENU
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bool "Virtio drivers"
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default y
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if VIRTIO_MENU
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config VIRTIO_HARDEN_NOTIFICATION
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bool "Harden virtio notification"
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depends on BROKEN
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help
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Enable this to harden the device notifications and suppress
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those that happen at a time where notifications are illegal.
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Experimental: Note that several drivers still have issues that
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may cause crashes or hangs when correct handling of
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notifications is enforced; depending on the subset of
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drivers and devices you use, this may or may not work.
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If unsure, say N.
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config VIRTIO_PCI
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tristate "PCI driver for virtio devices"
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depends on PCI
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select VIRTIO_PCI_LIB
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select VIRTIO
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help
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This driver provides support for virtio based paravirtual device
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drivers over PCI. This requires that your VMM has appropriate PCI
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virtio backends. Most QEMU based VMMs should support these devices
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(like KVM or Xen).
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If unsure, say M.
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config VIRTIO_PCI_ADMIN_LEGACY
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bool
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depends on VIRTIO_PCI && (X86 || COMPILE_TEST)
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default y
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config VIRTIO_PCI_LEGACY
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bool "Support for legacy virtio draft 0.9.X and older devices"
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default y
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depends on VIRTIO_PCI
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select VIRTIO_PCI_LIB_LEGACY
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help
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Virtio PCI Card 0.9.X Draft (circa 2014) and older device support.
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This option enables building a transitional driver, supporting
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both devices conforming to Virtio 1 specification, and legacy devices.
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If disabled, you get a slightly smaller, non-transitional driver,
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with no legacy compatibility.
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So look out into your driveway. Do you have a flying car? If
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so, you can happily disable this option and virtio will not
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break. Otherwise, leave it set. Unless you're testing what
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life will be like in The Future.
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If unsure, say Y.
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config VIRTIO_VDPA
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tristate "vDPA driver for virtio devices"
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depends on VDPA
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select VIRTIO
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help
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This driver provides support for virtio based paravirtual
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device driver over vDPA bus. For this to be useful, you need
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an appropriate vDPA device implementation that operates on a
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physical device to allow the datapath of virtio to be
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offloaded to hardware.
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If unsure, say M.
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config VIRTIO_PMEM
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tristate "Support for virtio pmem driver"
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depends on VIRTIO
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depends on LIBNVDIMM
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help
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This driver provides access to virtio-pmem devices, storage devices
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that are mapped into the physical address space - similar to NVDIMMs
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- with a virtio-based flushing interface.
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If unsure, say Y.
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config VIRTIO_BALLOON
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tristate "Virtio balloon driver"
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depends on VIRTIO
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select MEMORY_BALLOON
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select PAGE_REPORTING
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help
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This driver supports increasing and decreasing the amount
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of memory within a KVM guest.
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If unsure, say M.
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config VIRTIO_MEM
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tristate "Virtio mem driver"
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depends on X86_64 || ARM64 || RISCV || S390
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depends on VIRTIO
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depends on MEMORY_HOTPLUG
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depends on MEMORY_HOTREMOVE
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depends on CONTIG_ALLOC
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depends on EXCLUSIVE_SYSTEM_RAM
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help
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This driver provides access to virtio-mem paravirtualized memory
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devices, allowing to hotplug and hotunplug memory.
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This driver currently supports x86-64, arm64, riscv and s390.
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Although it should compile on other architectures that implement
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memory hot(un)plug, architecture-specific and/or common
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code changes may be required for virtio-mem, kdump and kexec to
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work as expected.
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If unsure, say M.
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config VIRTIO_INPUT
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tristate "Virtio input driver"
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depends on VIRTIO
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depends on INPUT
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help
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This driver supports virtio input devices such as
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keyboards, mice and tablets.
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If unsure, say M.
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config VIRTIO_MMIO
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tristate "Platform bus driver for memory mapped virtio devices"
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depends on HAS_IOMEM && HAS_DMA
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select VIRTIO
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help
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This drivers provides support for memory mapped virtio
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platform device driver.
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If unsure, say N.
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config VIRTIO_MMIO_CMDLINE_DEVICES
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bool "Memory mapped virtio devices parameter parsing"
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depends on VIRTIO_MMIO
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help
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Allow virtio-mmio devices instantiation via the kernel command line
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or module parameters. Be aware that using incorrect parameters (base
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address in particular) can crash your system - you have been warned.
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See Documentation/admin-guide/kernel-parameters.rst for details.
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If unsure, say 'N'.
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config VIRTIO_DMA_SHARED_BUFFER
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tristate
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depends on DMA_SHARED_BUFFER
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help
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This option adds a flavor of dma buffers that are backed by
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virtio resources.
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config VIRTIO_DEBUG
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bool "Debug facilities"
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depends on VIRTIO
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help
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Enable this to expose debug facilities over debugfs.
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This allows to debug features, to see what features the device
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advertises and to set filter for features used by driver.
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If unsure, say N.
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config VIRTIO_RTC
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tristate "Virtio RTC driver"
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depends on VIRTIO
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depends on PTP_1588_CLOCK_OPTIONAL
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help
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This driver provides current time from a Virtio RTC device. The driver
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provides the time through one or more clocks. The Virtio RTC PTP
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clocks and/or the Real Time Clock driver for Virtio RTC must be
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enabled to expose the clocks to userspace.
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To compile this code as a module, choose M here: the module will be
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called virtio_rtc.
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If unsure, say M.
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if VIRTIO_RTC
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comment "WARNING: Consider enabling VIRTIO_RTC_PTP and/or VIRTIO_RTC_CLASS."
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depends on !VIRTIO_RTC_PTP && !VIRTIO_RTC_CLASS
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comment "Enable PTP_1588_CLOCK in order to enable VIRTIO_RTC_PTP."
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depends on PTP_1588_CLOCK=n
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config VIRTIO_RTC_PTP
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bool "Virtio RTC PTP clocks"
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default y
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depends on PTP_1588_CLOCK
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help
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This exposes any Virtio RTC clocks as PTP Hardware Clocks (PHCs) to
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userspace. The PHC sysfs attribute "clock_name" describes the clock
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type.
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If unsure, say Y.
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config VIRTIO_RTC_ARM
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bool "Virtio RTC cross-timestamping using Arm Generic Timer"
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default y
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depends on VIRTIO_RTC_PTP && ARM_ARCH_TIMER
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help
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This enables Virtio RTC cross-timestamping using the Arm Generic Timer.
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It only has an effect if the Virtio RTC device also supports this. The
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cross-timestamp is available through the PTP clock driver precise
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cross-timestamp ioctl (PTP_SYS_OFFSET_PRECISE2 aka
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PTP_SYS_OFFSET_PRECISE).
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If unsure, say Y.
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comment "Enable RTC_CLASS in order to enable VIRTIO_RTC_CLASS."
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depends on RTC_CLASS=n
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config VIRTIO_RTC_CLASS
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bool "Real Time Clock driver for Virtio RTC"
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default y
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depends on RTC_CLASS
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help
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This exposes the Virtio RTC UTC-like clock as a Linux Real Time Clock.
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It only has an effect if the Virtio RTC device has a UTC-like clock
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which smears leap seconds to avoid steps. The Real Time Clock is
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read-only, and may support setting an alarm.
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If unsure, say Y.
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endif # VIRTIO_RTC
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endif # VIRTIO_MENU
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