arch/src/lib.rs

// Copyright 2018 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

//! Virtual machine architecture support code.

pub mod android;
pub mod fdt;
pub mod pstore;
pub mod serial;

pub mod sys;

use std::collections::BTreeMap;
use std::error::Error as StdError;
use std::fs::File;
use std::io;
use std::ops::Deref;
use std::path::PathBuf;
use std::str::FromStr;
use std::sync::mpsc;
use std::sync::mpsc::SendError;
use std::sync::Arc;

use acpi_tables::sdt::SDT;
use base::syslog;
use base::AsRawDescriptors;
use base::FileGetLen;
use base::FileReadWriteAtVolatile;
use base::RecvTube;
use base::SendTube;
use base::Tube;
use devices::virtio::VirtioDevice;
use devices::BarRange;
use devices::Bus;
use devices::BusDevice;
use devices::BusDeviceObj;
use devices::BusError;
use devices::BusResumeDevice;
use devices::FwCfgParameters;
use devices::GpeScope;
use devices::HotPlugBus;
use devices::IrqChip;
use devices::IrqEventSource;
use devices::PciAddress;
use devices::PciBus;
use devices::PciDevice;
use devices::PciDeviceError;
use devices::PciInterruptPin;
use devices::PciRoot;
use devices::PciRootCommand;
use devices::PreferredIrq;
#[cfg(any(target_os = "android", target_os = "linux"))]
use devices::ProxyDevice;
use devices::SerialHardware;
use devices::SerialParameters;
pub use fdt::apply_device_tree_overlays;
pub use fdt::DtbOverlay;
#[cfg(feature = "gdb")]
use gdbstub::arch::Arch;
use hypervisor::MemCacheType;
use hypervisor::Vm;
#[cfg(windows)]
use jail::FakeMinijailStub as Minijail;
#[cfg(any(target_os = "android", target_os = "linux"))]
use minijail::Minijail;
use remain::sorted;
use resources::SystemAllocator;
use resources::SystemAllocatorConfig;
use serde::de::Visitor;
use serde::Deserialize;
use serde::Serialize;
use serde_keyvalue::FromKeyValues;
pub use serial::add_serial_devices;
pub use serial::get_serial_cmdline;
pub use serial::set_default_serial_parameters;
pub use serial::GetSerialCmdlineError;
pub use serial::SERIAL_ADDR;
use sync::Condvar;
use sync::Mutex;
#[cfg(any(target_os = "android", target_os = "linux"))]
pub use sys::linux::PlatformBusResources;
use thiserror::Error;
use uuid::Uuid;
use vm_control::BatControl;
use vm_control::BatteryType;
use vm_control::PmResource;
use vm_memory::GuestAddress;
use vm_memory::GuestMemory;
use vm_memory::GuestMemoryError;
use vm_memory::MemoryRegionInformation;
use vm_memory::MemoryRegionOptions;

cfg_if::cfg_if! {
    if #[cfg(any(target_arch = "arm", target_arch = "aarch64"))] {
        pub use devices::IrqChipAArch64 as IrqChipArch;
        #[cfg(feature = "gdb")]
        pub use gdbstub_arch::aarch64::AArch64 as GdbArch;
        pub use hypervisor::CpuConfigAArch64 as CpuConfigArch;
        pub use hypervisor::Hypervisor as HypervisorArch;
        pub use hypervisor::VcpuAArch64 as VcpuArch;
        pub use hypervisor::VcpuInitAArch64 as VcpuInitArch;
        pub use hypervisor::VmAArch64 as VmArch;
    } else if #[cfg(target_arch = "riscv64")] {
        pub use devices::IrqChipRiscv64 as IrqChipArch;
        #[cfg(feature = "gdb")]
        pub use gdbstub_arch::riscv::Riscv64 as GdbArch;
        pub use hypervisor::CpuConfigRiscv64 as CpuConfigArch;
        pub use hypervisor::Hypervisor as HypervisorArch;
        pub use hypervisor::VcpuInitRiscv64 as VcpuInitArch;
        pub use hypervisor::VcpuRiscv64 as VcpuArch;
        pub use hypervisor::VmRiscv64 as VmArch;
    } else if #[cfg(target_arch = "x86_64")] {
        pub use devices::IrqChipX86_64 as IrqChipArch;
        #[cfg(feature = "gdb")]
        pub use gdbstub_arch::x86::X86_64_SSE as GdbArch;
        pub use hypervisor::CpuConfigX86_64 as CpuConfigArch;
        pub use hypervisor::HypervisorX86_64 as HypervisorArch;
        pub use hypervisor::VcpuInitX86_64 as VcpuInitArch;
        pub use hypervisor::VcpuX86_64 as VcpuArch;
        pub use hypervisor::VmX86_64 as VmArch;
    }
}

pub enum VmImage {
    Kernel(File),
    Bios(File),
}

#[derive(Clone, Debug, Deserialize, Serialize, FromKeyValues, PartialEq, Eq)]
#[serde(deny_unknown_fields, rename_all = "kebab-case")]
pub struct Pstore {
    pub path: PathBuf,
    pub size: u32,
}

#[derive(Clone, Copy, Debug, Serialize, Deserialize, FromKeyValues)]
#[serde(deny_unknown_fields, rename_all = "kebab-case")]
pub enum FdtPosition {
    /// At the start of RAM.
    Start,
    /// Near the end of RAM.
    End,
    /// After the payload, with some padding for alignment.
    AfterPayload,
}

/// Set of CPU cores.
#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
pub struct CpuSet(Vec<usize>);

impl CpuSet {
    pub fn new<I: IntoIterator<Item = usize>>(cpus: I) -> Self {
        CpuSet(cpus.into_iter().collect())
    }

    pub fn iter(&self) -> std::slice::Iter<'_, usize> {
        self.0.iter()
    }
}

impl FromIterator<usize> for CpuSet {
    fn from_iter<T>(iter: T) -> Self
    where
        T: IntoIterator<Item = usize>,
    {
        CpuSet::new(iter)
    }
}

/// The SVE config for Vcpus.
#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Deserialize, Serialize)]
#[serde(deny_unknown_fields, rename_all = "kebab-case")]
pub struct SveConfig {
    /// Use SVE
    #[serde(default)]
    pub enable: bool,
    /// Detect if SVE is available and enable accordingly. `enable` is ignored if auto is true
    #[serde(default)]
    pub auto: bool,
}

fn parse_cpu_range(s: &str, cpuset: &mut Vec<usize>) -> Result<(), String> {
    fn parse_cpu(s: &str) -> Result<usize, String> {
        s.parse().map_err(|_| {
            format!(
                "invalid CPU index {} - index must be a non-negative integer",
                s
            )
        })
    }

    let (first_cpu, last_cpu) = match s.split_once('-') {
        Some((first_cpu, last_cpu)) => {
            let first_cpu = parse_cpu(first_cpu)?;
            let last_cpu = parse_cpu(last_cpu)?;

            if last_cpu < first_cpu {
                return Err(format!(
                    "invalid CPU range {} - ranges must be from low to high",
                    s
                ));
            }
            (first_cpu, last_cpu)
        }
        None => {
            let cpu = parse_cpu(s)?;
            (cpu, cpu)
        }
    };

    cpuset.extend(first_cpu..=last_cpu);

    Ok(())
}

impl FromStr for CpuSet {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut cpuset = Vec::new();
        for part in s.split(',') {
            parse_cpu_range(part, &mut cpuset)?;
        }
        Ok(CpuSet::new(cpuset))
    }
}

impl Deref for CpuSet {
    type Target = Vec<usize>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl IntoIterator for CpuSet {
    type Item = usize;
    type IntoIter = std::vec::IntoIter<Self::Item>;

    fn into_iter(self) -> Self::IntoIter {
        self.0.into_iter()
    }
}

/// Deserializes a `CpuSet` from a sequence which elements can either be integers, or strings
/// representing CPU ranges (e.g. `5-8`).
impl<'de> Deserialize<'de> for CpuSet {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        struct CpuSetVisitor;
        impl<'de> Visitor<'de> for CpuSetVisitor {
            type Value = CpuSet;

            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
                formatter.write_str("CpuSet")
            }

            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
            where
                A: serde::de::SeqAccess<'de>,
            {
                #[derive(Deserialize)]
                #[serde(untagged)]
                enum CpuSetValue<'a> {
                    Single(usize),
                    Range(&'a str),
                }

                let mut cpus = Vec::new();
                while let Some(cpuset) = seq.next_element::<CpuSetValue>()? {
                    match cpuset {
                        CpuSetValue::Single(cpu) => cpus.push(cpu),
                        CpuSetValue::Range(range) => {
                            parse_cpu_range(range, &mut cpus).map_err(serde::de::Error::custom)?;
                        }
                    }
                }

                Ok(CpuSet::new(cpus))
            }
        }

        deserializer.deserialize_seq(CpuSetVisitor)
    }
}

/// Serializes a `CpuSet` into a sequence of integers and strings representing CPU ranges.
impl Serialize for CpuSet {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        use serde::ser::SerializeSeq;

        let mut seq = serializer.serialize_seq(None)?;

        // Factorize ranges into "a-b" strings.
        let mut serialize_range = |start: usize, end: usize| -> Result<(), S::Error> {
            if start == end {
                seq.serialize_element(&start)?;
            } else {
                seq.serialize_element(&format!("{}-{}", start, end))?;
            }

            Ok(())
        };

        // Current range.
        let mut range = None;
        for core in &self.0 {
            range = match range {
                None => Some((core, core)),
                Some((start, end)) if *end == *core - 1 => Some((start, core)),
                Some((start, end)) => {
                    serialize_range(*start, *end)?;
                    Some((core, core))
                }
            };
        }

        if let Some((start, end)) = range {
            serialize_range(*start, *end)?;
        }

        seq.end()
    }
}

/// Mapping of guest VCPU threads to host CPU cores.
#[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
pub enum VcpuAffinity {
    /// All VCPU threads will be pinned to the same set of host CPU cores.
    Global(CpuSet),
    /// Each VCPU may be pinned to a set of host CPU cores.
    /// The map key is a guest VCPU index, and the corresponding value is the set of
    /// host CPU indices that the VCPU thread will be allowed to run on.
    /// If a VCPU index is not present in the map, its affinity will not be set.
    PerVcpu(BTreeMap<usize, CpuSet>),
}

/// Memory region with optional size.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize, FromKeyValues)]
pub struct MemoryRegionConfig {
    pub start: u64,
    pub size: Option<u64>,
}

/// General PCI config.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize, FromKeyValues)]
pub struct PciConfig {
    /// region for PCI Configuration Access Mechanism
    #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
    pub cam: Option<MemoryRegionConfig>,
    /// region for PCIe Enhanced Configuration Access Mechanism
    #[cfg(target_arch = "x86_64")]
    pub ecam: Option<MemoryRegionConfig>,
    /// region for non-prefetchable PCI device memory below 4G
    pub mem: Option<MemoryRegionConfig>,
}

/// Holds the pieces needed to build a VM. Passed to `build_vm` in the `LinuxArch` trait below to
/// create a `RunnableLinuxVm`.
#[sorted]
pub struct VmComponents {
    #[cfg(all(target_arch = "x86_64", unix))]
    pub ac_adapter: bool,
    pub acpi_sdts: Vec<SDT>,
    pub android_fstab: Option<File>,
    pub boot_cpu: usize,
    pub bootorder_fw_cfg_blob: Vec<u8>,
    #[cfg(target_arch = "x86_64")]
    pub break_linux_pci_config_io: bool,
    pub cpu_capacity: BTreeMap<usize, u32>,
    pub cpu_clusters: Vec<CpuSet>,
    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        any(target_os = "android", target_os = "linux")
    ))]
    pub cpu_frequencies: BTreeMap<usize, Vec<u32>>,
    pub delay_rt: bool,
    pub dynamic_power_coefficient: BTreeMap<usize, u32>,
    pub extra_kernel_params: Vec<String>,
    #[cfg(target_arch = "x86_64")]
    pub force_s2idle: bool,
    pub fw_cfg_enable: bool,
    pub fw_cfg_parameters: Vec<FwCfgParameters>,
    pub host_cpu_topology: bool,
    pub hugepages: bool,
    pub hv_cfg: hypervisor::Config,
    pub initrd_image: Option<File>,
    pub itmt: bool,
    pub memory_size: u64,
    pub no_i8042: bool,
    pub no_rtc: bool,
    pub no_smt: bool,
    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        any(target_os = "android", target_os = "linux")
    ))]
    pub normalized_cpu_ipc_ratios: BTreeMap<usize, u32>,
    pub pci_config: PciConfig,
    pub pflash_block_size: u32,
    pub pflash_image: Option<File>,
    pub pstore: Option<Pstore>,
    /// A file to load as pVM firmware. Must be `Some` iff
    /// `hv_cfg.protection_type == ProtectionType::UnprotectedWithFirmware`.
    pub pvm_fw: Option<File>,
    pub rt_cpus: CpuSet,
    #[cfg(target_arch = "x86_64")]
    pub smbios: SmbiosOptions,
    #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
    pub sve_config: SveConfig,
    pub swiotlb: Option<u64>,
    pub vcpu_affinity: Option<VcpuAffinity>,
    pub vcpu_count: usize,
    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        any(target_os = "android", target_os = "linux")
    ))]
    pub vcpu_domain_paths: BTreeMap<usize, PathBuf>,
    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        any(target_os = "android", target_os = "linux")
    ))]
    pub vcpu_domains: BTreeMap<usize, u32>,
    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        any(target_os = "android", target_os = "linux")
    ))]
    pub virt_cpufreq_v2: bool,
    pub vm_image: VmImage,
}

/// Holds the elements needed to run a Linux VM. Created by `build_vm`.
#[sorted]
pub struct RunnableLinuxVm<V: VmArch, Vcpu: VcpuArch> {
    pub bat_control: Option<BatControl>,
    pub delay_rt: bool,
    pub devices_thread: Option<std::thread::JoinHandle<()>>,
    pub hotplug_bus: BTreeMap<u8, Arc<Mutex<dyn HotPlugBus>>>,
    pub io_bus: Arc<Bus>,
    pub irq_chip: Box<dyn IrqChipArch>,
    pub mmio_bus: Arc<Bus>,
    pub no_smt: bool,
    pub pid_debug_label_map: BTreeMap<u32, String>,
    #[cfg(any(target_os = "android", target_os = "linux"))]
    pub platform_devices: Vec<Arc<Mutex<dyn BusDevice>>>,
    pub pm: Option<Arc<Mutex<dyn PmResource + Send>>>,
    /// Devices to be notified before the system resumes from the S3 suspended state.
    pub resume_notify_devices: Vec<Arc<Mutex<dyn BusResumeDevice>>>,
    pub root_config: Arc<Mutex<PciRoot>>,
    pub rt_cpus: CpuSet,
    pub suspend_tube: (Arc<Mutex<SendTube>>, RecvTube),
    pub vcpu_affinity: Option<VcpuAffinity>,
    pub vcpu_count: usize,
    pub vcpu_init: Vec<VcpuInitArch>,
    /// If vcpus is None, then it's the responsibility of the vcpu thread to create vcpus.
    /// If it's Some, then `build_vm` already created the vcpus.
    pub vcpus: Option<Vec<Vcpu>>,
    pub vm: V,
    pub vm_request_tubes: Vec<Tube>,
}

/// The device and optional jail.
pub struct VirtioDeviceStub {
    pub dev: Box<dyn VirtioDevice>,
    pub jail: Option<Minijail>,
}

/// Trait which is implemented for each Linux Architecture in order to
/// set up the memory, cpus, and system devices and to boot the kernel.
pub trait LinuxArch {
    type Error: StdError;
    type ArchMemoryLayout;

    /// Decide architecture specific memory layout details to be used by later stages of the VM
    /// setup.
    fn arch_memory_layout(
        components: &VmComponents,
    ) -> std::result::Result<Self::ArchMemoryLayout, Self::Error>;

    /// Returns a Vec of the valid memory addresses as pairs of address and length. These should be
    /// used to configure the `GuestMemory` structure for the platform.
    ///
    /// # Arguments
    ///
    /// * `components` - Parts used to determine the memory layout.
    fn guest_memory_layout(
        components: &VmComponents,
        arch_memory_layout: &Self::ArchMemoryLayout,
        hypervisor: &impl hypervisor::Hypervisor,
    ) -> std::result::Result<Vec<(GuestAddress, u64, MemoryRegionOptions)>, Self::Error>;

    /// Gets the configuration for a new `SystemAllocator` that fits the given `Vm`'s memory layout.
    ///
    /// This is the per-architecture template for constructing the `SystemAllocator`. Platform
    /// agnostic modifications may be made to this configuration, but the final `SystemAllocator`
    /// will be at least as strict as this configuration.
    ///
    /// # Arguments
    ///
    /// * `vm` - The virtual machine to be used as a template for the `SystemAllocator`.
    fn get_system_allocator_config<V: Vm>(
        vm: &V,
        arch_memory_layout: &Self::ArchMemoryLayout,
    ) -> SystemAllocatorConfig;

    /// Takes `VmComponents` and generates a `RunnableLinuxVm`.
    ///
    /// # Arguments
    ///
    /// * `components` - Parts to use to build the VM.
    /// * `vm_evt_wrtube` - Tube used by sub-devices to request that crosvm exit because guest wants
    ///   to stop/shut down or requested reset.
    /// * `system_allocator` - Allocator created by this trait's implementation of
    ///   `get_system_allocator_config`.
    /// * `serial_parameters` - Definitions for how the serial devices should be configured.
    /// * `serial_jail` - Jail used for serial devices created here.
    /// * `battery` - Defines what battery device will be created.
    /// * `vm` - A VM implementation to build upon.
    /// * `ramoops_region` - Region allocated for ramoops.
    /// * `devices` - The devices to be built into the VM.
    /// * `irq_chip` - The IRQ chip implemention for the VM.
    /// * `debugcon_jail` - Jail used for debugcon devices created here.
    /// * `pflash_jail` - Jail used for pflash device created here.
    /// * `fw_cfg_jail` - Jail used for fw_cfg device created here.
    /// * `device_tree_overlays` - Device tree overlay binaries
    fn build_vm<V, Vcpu>(
        components: VmComponents,
        arch_memory_layout: &Self::ArchMemoryLayout,
        vm_evt_wrtube: &SendTube,
        system_allocator: &mut SystemAllocator,
        serial_parameters: &BTreeMap<(SerialHardware, u8), SerialParameters>,
        serial_jail: Option<Minijail>,
        battery: (Option<BatteryType>, Option<Minijail>),
        vm: V,
        ramoops_region: Option<pstore::RamoopsRegion>,
        devices: Vec<(Box<dyn BusDeviceObj>, Option<Minijail>)>,
        irq_chip: &mut dyn IrqChipArch,
        vcpu_ids: &mut Vec<usize>,
        dump_device_tree_blob: Option<PathBuf>,
        debugcon_jail: Option<Minijail>,
        #[cfg(target_arch = "x86_64")] pflash_jail: Option<Minijail>,
        #[cfg(target_arch = "x86_64")] fw_cfg_jail: Option<Minijail>,
        #[cfg(feature = "swap")] swap_controller: &mut Option<swap::SwapController>,
        guest_suspended_cvar: Option<Arc<(Mutex<bool>, Condvar)>>,
        device_tree_overlays: Vec<DtbOverlay>,
        fdt_position: Option<FdtPosition>,
        no_pmu: bool,
    ) -> std::result::Result<RunnableLinuxVm<V, Vcpu>, Self::Error>
    where
        V: VmArch,
        Vcpu: VcpuArch;

    /// Configures the vcpu and should be called once per vcpu from the vcpu's thread.
    ///
    /// # Arguments
    ///
    /// * `vm` - The virtual machine object.
    /// * `hypervisor` - The `Hypervisor` that created the vcpu.
    /// * `irq_chip` - The `IrqChip` associated with this vm.
    /// * `vcpu` - The VCPU object to configure.
    /// * `vcpu_init` - The data required to initialize VCPU registers and other state.
    /// * `vcpu_id` - The id of the given `vcpu`.
    /// * `num_cpus` - Number of virtual CPUs the guest will have.
    /// * `cpu_config` - CPU feature configurations.
    fn configure_vcpu<V: Vm>(
        vm: &V,
        hypervisor: &dyn HypervisorArch,
        irq_chip: &mut dyn IrqChipArch,
        vcpu: &mut dyn VcpuArch,
        vcpu_init: VcpuInitArch,
        vcpu_id: usize,
        num_cpus: usize,
        cpu_config: Option<CpuConfigArch>,
    ) -> Result<(), Self::Error>;

    /// Configures and add a pci device into vm
    fn register_pci_device<V: VmArch, Vcpu: VcpuArch>(
        linux: &mut RunnableLinuxVm<V, Vcpu>,
        device: Box<dyn PciDevice>,
        #[cfg(any(target_os = "android", target_os = "linux"))] minijail: Option<Minijail>,
        resources: &mut SystemAllocator,
        hp_control_tube: &mpsc::Sender<PciRootCommand>,
        #[cfg(feature = "swap")] swap_controller: &mut Option<swap::SwapController>,
    ) -> Result<PciAddress, Self::Error>;

    /// Returns frequency map for each of the host's logical cores.
    fn get_host_cpu_frequencies_khz() -> Result<BTreeMap<usize, Vec<u32>>, Self::Error>;

    /// Returns max-freq map of the host's logical cores.
    fn get_host_cpu_max_freq_khz() -> Result<BTreeMap<usize, u32>, Self::Error>;

    /// Returns capacity map of the host's logical cores.
    fn get_host_cpu_capacity() -> Result<BTreeMap<usize, u32>, Self::Error>;

    /// Returns cluster masks for each of the host's logical cores.
    fn get_host_cpu_clusters() -> Result<Vec<CpuSet>, Self::Error>;
}

#[cfg(feature = "gdb")]
pub trait GdbOps<T: VcpuArch> {
    type Error: StdError;

    /// Reads vCPU's registers.
    fn read_registers(vcpu: &T) -> Result<<GdbArch as Arch>::Registers, Self::Error>;

    /// Writes vCPU's registers.
    fn write_registers(vcpu: &T, regs: &<GdbArch as Arch>::Registers) -> Result<(), Self::Error>;

    /// Reads bytes from the guest memory.
    fn read_memory(
        vcpu: &T,
        guest_mem: &GuestMemory,
        vaddr: GuestAddress,
        len: usize,
    ) -> Result<Vec<u8>, Self::Error>;

    /// Writes bytes to the specified guest memory.
    fn write_memory(
        vcpu: &T,
        guest_mem: &GuestMemory,
        vaddr: GuestAddress,
        buf: &[u8],
    ) -> Result<(), Self::Error>;

    /// Reads bytes from the guest register.
    ///
    /// Returns an empty vector if `reg_id` is valid but the register is not available.
    fn read_register(vcpu: &T, reg_id: <GdbArch as Arch>::RegId) -> Result<Vec<u8>, Self::Error>;

    /// Writes bytes to the specified guest register.
    fn write_register(
        vcpu: &T,
        reg_id: <GdbArch as Arch>::RegId,
        data: &[u8],
    ) -> Result<(), Self::Error>;

    /// Make the next vCPU's run single-step.
    fn enable_singlestep(vcpu: &T) -> Result<(), Self::Error>;

    /// Get maximum number of hardware breakpoints.
    fn get_max_hw_breakpoints(vcpu: &T) -> Result<usize, Self::Error>;

    /// Set hardware breakpoints at the given addresses.
    fn set_hw_breakpoints(vcpu: &T, breakpoints: &[GuestAddress]) -> Result<(), Self::Error>;
}

/// Errors for device manager.
#[sorted]
#[derive(Error, Debug)]
pub enum DeviceRegistrationError {
    /// No more MMIO space available.
    #[error("no more addresses are available")]
    AddrsExhausted,
    /// Could not allocate device address space for the device.
    #[error("Allocating device addresses: {0}")]
    AllocateDeviceAddrs(PciDeviceError),
    /// Could not allocate IO space for the device.
    #[error("Allocating IO addresses: {0}")]
    AllocateIoAddrs(PciDeviceError),
    /// Could not allocate MMIO or IO resource for the device.
    #[error("Allocating IO resource: {0}")]
    AllocateIoResource(resources::Error),
    /// Could not allocate an IRQ number.
    #[error("Allocating IRQ number")]
    AllocateIrq,
    /// Could not allocate IRQ resource for the device.
    #[cfg(any(target_os = "android", target_os = "linux"))]
    #[error("Allocating IRQ resource: {0}")]
    AllocateIrqResource(devices::vfio::VfioError),
    /// Broken pci topology
    #[error("pci topology is broken")]
    BrokenPciTopology,
    /// Unable to clone a jail for the device.
    #[cfg(any(target_os = "android", target_os = "linux"))]
    #[error("failed to clone jail: {0}")]
    CloneJail(minijail::Error),
    /// Appending to kernel command line failed.
    #[error("unable to add device to kernel command line: {0}")]
    Cmdline(kernel_cmdline::Error),
    /// Configure window size failed.
    #[error("failed to configure window size: {0}")]
    ConfigureWindowSize(PciDeviceError),
    // Unable to create a pipe.
    #[error("failed to create pipe: {0}")]
    CreatePipe(base::Error),
    // Unable to create a root.
    #[error("failed to create pci root: {0}")]
    CreateRoot(anyhow::Error),
    // Unable to create serial device from serial parameters
    #[error("failed to create serial device: {0}")]
    CreateSerialDevice(devices::SerialError),
    // Unable to create tube
    #[error("failed to create tube: {0}")]
    CreateTube(base::TubeError),
    /// Could not clone an event.
    #[error("failed to clone event: {0}")]
    EventClone(base::Error),
    /// Could not create an event.
    #[error("failed to create event: {0}")]
    EventCreate(base::Error),
    /// Failed to generate ACPI content.
    #[error("failed to generate ACPI content")]
    GenerateAcpi,
    /// No more IRQs are available.
    #[error("no more IRQs are available")]
    IrqsExhausted,
    /// VFIO device is missing a DT symbol.
    #[error("cannot match VFIO device to DT node due to a missing symbol")]
    MissingDeviceTreeSymbol,
    /// Missing a required serial device.
    #[error("missing required serial device {0}")]
    MissingRequiredSerialDevice(u8),
    /// Could not add a device to the mmio bus.
    #[error("failed to add to mmio bus: {0}")]
    MmioInsert(BusError),
    /// Failed to insert device into PCI root.
    #[error("failed to insert device into PCI root: {0}")]
    PciRootAddDevice(PciDeviceError),
    #[cfg(any(target_os = "android", target_os = "linux"))]
    /// Failed to initialize proxy device for jailed device.
    #[error("failed to create proxy device: {0}")]
    ProxyDeviceCreation(devices::ProxyError),
    #[cfg(any(target_os = "android", target_os = "linux"))]
    /// Failed to register battery device.
    #[error("failed to register battery device to VM: {0}")]
    RegisterBattery(devices::BatteryError),
    /// Could not register PCI device to pci root bus
    #[error("failed to register PCI device to pci root bus")]
    RegisterDevice(SendError<PciRootCommand>),
    /// Could not register PCI device capabilities.
    #[error("could not register PCI device capabilities: {0}")]
    RegisterDeviceCapabilities(PciDeviceError),
    /// Failed to register ioevent with VM.
    #[error("failed to register ioevent to VM: {0}")]
    RegisterIoevent(base::Error),
    /// Failed to register irq event with VM.
    #[error("failed to register irq event to VM: {0}")]
    RegisterIrqfd(base::Error),
    /// Could not setup VFIO platform IRQ for the device.
    #[error("Setting up VFIO platform IRQ: {0}")]
    SetupVfioPlatformIrq(anyhow::Error),
}

/// Config a PCI device for used by this vm.
pub fn configure_pci_device<V: VmArch, Vcpu: VcpuArch>(
    linux: &mut RunnableLinuxVm<V, Vcpu>,
    mut device: Box<dyn PciDevice>,
    #[cfg(any(target_os = "android", target_os = "linux"))] jail: Option<Minijail>,
    resources: &mut SystemAllocator,
    hp_control_tube: &mpsc::Sender<PciRootCommand>,
    #[cfg(feature = "swap")] swap_controller: &mut Option<swap::SwapController>,
) -> Result<PciAddress, DeviceRegistrationError> {
    // Allocate PCI device address before allocating BARs.
    let pci_address = device
        .allocate_address(resources)
        .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;

    // Allocate ranges that may need to be in the low MMIO region (MmioType::Low).
    let mmio_ranges = device
        .allocate_io_bars(resources)
        .map_err(DeviceRegistrationError::AllocateIoAddrs)?;

    // Allocate device ranges that may be in low or high MMIO after low-only ranges.
    let device_ranges = device
        .allocate_device_bars(resources)
        .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;

    // If device is a pcie bridge, add its pci bus to pci root
    if let Some(pci_bus) = device.get_new_pci_bus() {
        hp_control_tube
            .send(PciRootCommand::AddBridge(pci_bus))
            .map_err(DeviceRegistrationError::RegisterDevice)?;
        let bar_ranges = Vec::new();
        device
            .configure_bridge_window(resources, &bar_ranges)
            .map_err(DeviceRegistrationError::ConfigureWindowSize)?;
    }

    // Do not suggest INTx for hot-plug devices.
    let intx_event = devices::IrqLevelEvent::new().map_err(DeviceRegistrationError::EventCreate)?;

    if let PreferredIrq::Fixed { pin, gsi } = device.preferred_irq() {
        resources.reserve_irq(gsi);

        device.assign_irq(
            intx_event
                .try_clone()
                .map_err(DeviceRegistrationError::EventClone)?,
            pin,
            gsi,
        );

        linux
            .irq_chip
            .as_irq_chip_mut()
            .register_level_irq_event(gsi, &intx_event, IrqEventSource::from_device(&device))
            .map_err(DeviceRegistrationError::RegisterIrqfd)?;
    }

    let mut keep_rds = device.keep_rds();
    syslog::push_descriptors(&mut keep_rds);
    cros_tracing::push_descriptors!(&mut keep_rds);
    metrics::push_descriptors(&mut keep_rds);

    device
        .register_device_capabilities()
        .map_err(DeviceRegistrationError::RegisterDeviceCapabilities)?;

    #[cfg(any(target_os = "android", target_os = "linux"))]
    let arced_dev: Arc<Mutex<dyn BusDevice>> = if let Some(jail) = jail {
        let proxy = ProxyDevice::new(
            device,
            jail,
            keep_rds,
            #[cfg(feature = "swap")]
            swap_controller,
        )
        .map_err(DeviceRegistrationError::ProxyDeviceCreation)?;
        linux
            .pid_debug_label_map
            .insert(proxy.pid() as u32, proxy.debug_label());
        Arc::new(Mutex::new(proxy))
    } else {
        device.on_sandboxed();
        Arc::new(Mutex::new(device))
    };

    #[cfg(windows)]
    let arced_dev = {
        device.on_sandboxed();
        Arc::new(Mutex::new(device))
    };

    #[cfg(any(target_os = "android", target_os = "linux"))]
    hp_control_tube
        .send(PciRootCommand::Add(pci_address, arced_dev.clone()))
        .map_err(DeviceRegistrationError::RegisterDevice)?;

    for range in &mmio_ranges {
        linux
            .mmio_bus
            .insert(arced_dev.clone(), range.addr, range.size)
            .map_err(DeviceRegistrationError::MmioInsert)?;
    }

    for range in &device_ranges {
        linux
            .mmio_bus
            .insert(arced_dev.clone(), range.addr, range.size)
            .map_err(DeviceRegistrationError::MmioInsert)?;
    }

    Ok(pci_address)
}

// Generate pci topology starting from parent bus
fn generate_pci_topology(
    parent_bus: Arc<Mutex<PciBus>>,
    resources: &mut SystemAllocator,
    io_ranges: &mut BTreeMap<usize, Vec<BarRange>>,
    device_ranges: &mut BTreeMap<usize, Vec<BarRange>>,
    device_addrs: &[PciAddress],
    devices: &mut Vec<(Box<dyn PciDevice>, Option<Minijail>)>,
) -> Result<(Vec<BarRange>, u8), DeviceRegistrationError> {
    let mut bar_ranges = Vec::new();
    let bus_num = parent_bus.lock().get_bus_num();
    let mut subordinate_bus = bus_num;
    for (dev_idx, addr) in device_addrs.iter().enumerate() {
        // Only target for devices that located on this bus
        if addr.bus == bus_num {
            // If this device is a pci bridge (a.k.a., it has a pci bus structure),
            // create its topology recursively
            if let Some(child_bus) = devices[dev_idx].0.get_new_pci_bus() {
                let (child_bar_ranges, child_sub_bus) = generate_pci_topology(
                    child_bus.clone(),
                    resources,
                    io_ranges,
                    device_ranges,
                    device_addrs,
                    devices,
                )?;
                let device = &mut devices[dev_idx].0;
                parent_bus
                    .lock()
                    .add_child_bus(child_bus.clone())
                    .map_err(|_| DeviceRegistrationError::BrokenPciTopology)?;
                let bridge_window = device
                    .configure_bridge_window(resources, &child_bar_ranges)
                    .map_err(DeviceRegistrationError::ConfigureWindowSize)?;
                bar_ranges.extend(bridge_window);

                let ranges = device
                    .allocate_io_bars(resources)
                    .map_err(DeviceRegistrationError::AllocateIoAddrs)?;
                io_ranges.insert(dev_idx, ranges.clone());
                bar_ranges.extend(ranges);

                let ranges = device
                    .allocate_device_bars(resources)
                    .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;
                device_ranges.insert(dev_idx, ranges.clone());
                bar_ranges.extend(ranges);

                device.set_subordinate_bus(child_sub_bus);

                subordinate_bus = std::cmp::max(subordinate_bus, child_sub_bus);
            }
        }
    }

    for (dev_idx, addr) in device_addrs.iter().enumerate() {
        if addr.bus == bus_num {
            let device = &mut devices[dev_idx].0;
            // Allocate MMIO for non-bridge devices
            if device.get_new_pci_bus().is_none() {
                let ranges = device
                    .allocate_io_bars(resources)
                    .map_err(DeviceRegistrationError::AllocateIoAddrs)?;
                io_ranges.insert(dev_idx, ranges.clone());
                bar_ranges.extend(ranges);

                let ranges = device
                    .allocate_device_bars(resources)
                    .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;
                device_ranges.insert(dev_idx, ranges.clone());
                bar_ranges.extend(ranges);
            }
        }
    }
    Ok((bar_ranges, subordinate_bus))
}

/// Ensure all PCI devices have an assigned PCI address.
pub fn assign_pci_addresses(
    devices: &mut [(Box<dyn BusDeviceObj>, Option<Minijail>)],
    resources: &mut SystemAllocator,
) -> Result<(), DeviceRegistrationError> {
    // First allocate devices with a preferred address.
    for pci_device in devices
        .iter_mut()
        .filter_map(|(device, _jail)| device.as_pci_device_mut())
        .filter(|pci_device| pci_device.preferred_address().is_some())
    {
        let _ = pci_device
            .allocate_address(resources)
            .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;
    }

    // Then allocate addresses for the remaining devices.
    for pci_device in devices
        .iter_mut()
        .filter_map(|(device, _jail)| device.as_pci_device_mut())
        .filter(|pci_device| pci_device.preferred_address().is_none())
    {
        let _ = pci_device
            .allocate_address(resources)
            .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;
    }

    Ok(())
}

/// Creates a root PCI device for use by this Vm.
pub fn generate_pci_root(
    mut devices: Vec<(Box<dyn PciDevice>, Option<Minijail>)>,
    irq_chip: &mut dyn IrqChip,
    mmio_bus: Arc<Bus>,
    mmio_base: GuestAddress,
    mmio_register_bit_num: usize,
    io_bus: Arc<Bus>,
    resources: &mut SystemAllocator,
    vm: &mut impl Vm,
    max_irqs: usize,
    vcfg_base: Option<u64>,
    #[cfg(feature = "swap")] swap_controller: &mut Option<swap::SwapController>,
) -> Result<
    (
        PciRoot,
        Vec<(PciAddress, u32, PciInterruptPin)>,
        BTreeMap<u32, String>,
        BTreeMap<PciAddress, Vec<u8>>,
        BTreeMap<PciAddress, Vec<u8>>,
    ),
    DeviceRegistrationError,
> {
    let mut device_addrs = Vec::new();

    for (device, _jail) in devices.iter_mut() {
        let address = device
            .allocate_address(resources)
            .map_err(DeviceRegistrationError::AllocateDeviceAddrs)?;
        device_addrs.push(address);
    }

    let mut device_ranges = BTreeMap::new();
    let mut io_ranges = BTreeMap::new();
    let root_bus = Arc::new(Mutex::new(PciBus::new(0, 0, false)));

    generate_pci_topology(
        root_bus.clone(),
        resources,
        &mut io_ranges,
        &mut device_ranges,
        &device_addrs,
        &mut devices,
    )?;

    let mut root = PciRoot::new(
        vm,
        Arc::downgrade(&mmio_bus),
        mmio_base,
        mmio_register_bit_num,
        Arc::downgrade(&io_bus),
        root_bus,
    )
    .map_err(DeviceRegistrationError::CreateRoot)?;
    #[cfg_attr(windows, allow(unused_mut))]
    let mut pid_labels = BTreeMap::new();

    // Allocate legacy INTx
    let mut pci_irqs = Vec::new();
    let mut irqs: Vec<u32> = Vec::new();

    // Mapping of (bus, dev, pin) -> IRQ number.
    let mut dev_pin_irq = BTreeMap::new();

    for (dev_idx, (device, _jail)) in devices.iter_mut().enumerate() {
        let pci_address = device_addrs[dev_idx];

        let irq = match device.preferred_irq() {
            PreferredIrq::Fixed { pin, gsi } => {
                // The device reported a preferred IRQ, so use that rather than allocating one.
                resources.reserve_irq(gsi);
                Some((pin, gsi))
            }
            PreferredIrq::Any => {
                // The device did not provide a preferred IRQ but requested one, so allocate one.

                // Choose a pin based on the slot's function number. Function 0 must always use
                // INTA# for single-function devices per the PCI spec, and we choose to use INTA#
                // for function 0 on multifunction devices and distribute the remaining functions
                // evenly across the other pins.
                let pin = match pci_address.func % 4 {
                    0 => PciInterruptPin::IntA,
                    1 => PciInterruptPin::IntB,
                    2 => PciInterruptPin::IntC,
                    _ => PciInterruptPin::IntD,
                };

                // If an IRQ number has already been assigned for a different function with this
                // (bus, device, pin) combination, use it. Otherwise allocate a new one and insert
                // it into the map.
                let pin_key = (pci_address.bus, pci_address.dev, pin);
                let irq_num = if let Some(irq_num) = dev_pin_irq.get(&pin_key) {
                    *irq_num
                } else {
                    // If we have allocated fewer than `max_irqs` total, add a new irq to the `irqs`
                    // pool. Otherwise, share one of the existing `irqs`.
                    let irq_num = if irqs.len() < max_irqs {
                        let irq_num = resources
                            .allocate_irq()
                            .ok_or(DeviceRegistrationError::AllocateIrq)?;
                        irqs.push(irq_num);
                        irq_num
                    } else {
                        // Pick one of the existing IRQs to share, using `dev_idx` to distribute IRQ
                        // sharing evenly across devices.
                        irqs[dev_idx % max_irqs]
                    };

                    dev_pin_irq.insert(pin_key, irq_num);
                    irq_num
                };
                Some((pin, irq_num))
            }
            PreferredIrq::None => {
                // The device does not want an INTx# IRQ.
                None
            }
        };

        if let Some((pin, gsi)) = irq {
            let intx_event =
                devices::IrqLevelEvent::new().map_err(DeviceRegistrationError::EventCreate)?;

            device.assign_irq(
                intx_event
                    .try_clone()
                    .map_err(DeviceRegistrationError::EventClone)?,
                pin,
                gsi,
            );

            irq_chip
                .register_level_irq_event(gsi, &intx_event, IrqEventSource::from_device(device))
                .map_err(DeviceRegistrationError::RegisterIrqfd)?;

            pci_irqs.push((pci_address, gsi, pin));
        }
    }

    // To prevent issues where device's on_sandbox may spawn thread before all
    // sandboxed devices are sandboxed we partition iterator to go over sandboxed
    // first. This is needed on linux platforms. On windows, this is a no-op since
    // jails are always None, even for sandboxed devices.
    let devices = {
        let (sandboxed, non_sandboxed): (Vec<_>, Vec<_>) = devices
            .into_iter()
            .enumerate()
            .partition(|(_, (_, jail))| jail.is_some());
        sandboxed.into_iter().chain(non_sandboxed)
    };

    let mut amls = BTreeMap::new();
    let mut gpe_scope_amls = BTreeMap::new();
    for (dev_idx, dev_value) in devices {
        #[cfg(any(target_os = "android", target_os = "linux"))]
        let (mut device, jail) = dev_value;
        #[cfg(windows)]
        let (mut device, _) = dev_value;
        let address = device_addrs[dev_idx];

        let mut keep_rds = device.keep_rds();
        syslog::push_descriptors(&mut keep_rds);
        cros_tracing::push_descriptors!(&mut keep_rds);
        metrics::push_descriptors(&mut keep_rds);
        keep_rds.append(&mut vm.get_memory().as_raw_descriptors());

        let ranges = io_ranges.remove(&dev_idx).unwrap_or_default();
        let device_ranges = device_ranges.remove(&dev_idx).unwrap_or_default();
        device
            .register_device_capabilities()
            .map_err(DeviceRegistrationError::RegisterDeviceCapabilities)?;

        if let Some(vcfg_base) = vcfg_base {
            let (methods, shm) = device.generate_acpi_methods();
            if !methods.is_empty() {
                amls.insert(address, methods);
            }
            if let Some((offset, mmap)) = shm {
                let _ = vm.add_memory_region(
                    GuestAddress(vcfg_base + offset as u64),
                    Box::new(mmap),
                    false,
                    false,
                    MemCacheType::CacheCoherent,
                );
            }
        }
        let gpe_nr = device.set_gpe(resources);

        #[cfg(any(target_os = "android", target_os = "linux"))]
        let arced_dev: Arc<Mutex<dyn BusDevice>> = if let Some(jail) = jail {
            let proxy = ProxyDevice::new(
                device,
                jail,
                keep_rds,
                #[cfg(feature = "swap")]
                swap_controller,
            )
            .map_err(DeviceRegistrationError::ProxyDeviceCreation)?;
            pid_labels.insert(proxy.pid() as u32, proxy.debug_label());
            Arc::new(Mutex::new(proxy))
        } else {
            device.on_sandboxed();
            Arc::new(Mutex::new(device))
        };
        #[cfg(windows)]
        let arced_dev = {
            device.on_sandboxed();
            Arc::new(Mutex::new(device))
        };
        root.add_device(address, arced_dev.clone(), vm)
            .map_err(DeviceRegistrationError::PciRootAddDevice)?;
        for range in &ranges {
            mmio_bus
                .insert(arced_dev.clone(), range.addr, range.size)
                .map_err(DeviceRegistrationError::MmioInsert)?;
        }

        for range in &device_ranges {
            mmio_bus
                .insert(arced_dev.clone(), range.addr, range.size)
                .map_err(DeviceRegistrationError::MmioInsert)?;
        }

        if let Some(gpe_nr) = gpe_nr {
            if let Some(acpi_path) = root.acpi_path(&address) {
                let mut gpe_aml = Vec::new();

                GpeScope {}.cast_to_aml_bytes(
                    &mut gpe_aml,
                    gpe_nr,
                    format!("\\{}", acpi_path).as_str(),
                );
                if !gpe_aml.is_empty() {
                    gpe_scope_amls.insert(address, gpe_aml);
                }
            }
        }
    }

    Ok((root, pci_irqs, pid_labels, amls, gpe_scope_amls))
}

/// Errors for image loading.
#[sorted]
#[derive(Error, Debug)]
pub enum LoadImageError {
    #[error("Alignment not a power of two: {0}")]
    BadAlignment(u64),
    #[error("Getting image size failed: {0}")]
    GetLen(io::Error),
    #[error("GuestMemory get slice failed: {0}")]
    GuestMemorySlice(GuestMemoryError),
    #[error("Image size too large: {0}")]
    ImageSizeTooLarge(u64),
    #[error("No suitable memory region found")]
    NoSuitableMemoryRegion,
    #[error("Reading image into memory failed: {0}")]
    ReadToMemory(io::Error),
    #[error("Cannot load zero-sized image")]
    ZeroSizedImage,
}

/// Load an image from a file into guest memory.
///
/// # Arguments
///
/// * `guest_mem` - The memory to be used by the guest.
/// * `guest_addr` - The starting address to load the image in the guest memory.
/// * `max_size` - The amount of space in bytes available in the guest memory for the image.
/// * `image` - The file containing the image to be loaded.
///
/// The size in bytes of the loaded image is returned.
pub fn load_image<F>(
    guest_mem: &GuestMemory,
    image: &mut F,
    guest_addr: GuestAddress,
    max_size: u64,
) -> Result<usize, LoadImageError>
where
    F: FileReadWriteAtVolatile + FileGetLen,
{
    let size = image.get_len().map_err(LoadImageError::GetLen)?;

    if size > usize::MAX as u64 || size > max_size {
        return Err(LoadImageError::ImageSizeTooLarge(size));
    }

    // This is safe due to the bounds check above.
    let size = size as usize;

    let guest_slice = guest_mem
        .get_slice_at_addr(guest_addr, size)
        .map_err(LoadImageError::GuestMemorySlice)?;
    image
        .read_exact_at_volatile(guest_slice, 0)
        .map_err(LoadImageError::ReadToMemory)?;

    Ok(size)
}

/// Load an image from a file into guest memory at the highest possible address.
///
/// # Arguments
///
/// * `guest_mem` - The memory to be used by the guest.
/// * `image` - The file containing the image to be loaded.
/// * `min_guest_addr` - The minimum address of the start of the image.
/// * `max_guest_addr` - The address to load the last byte of the image.
/// * `region_filter` - The optional filter function for determining if the given guest memory
///   region is suitable for loading the image into it.
/// * `align` - The minimum alignment of the start address of the image in bytes (must be a power of
///   two).
///
/// The guest address and size in bytes of the loaded image are returned.
pub fn load_image_high<F>(
    guest_mem: &GuestMemory,
    image: &mut F,
    min_guest_addr: GuestAddress,
    max_guest_addr: GuestAddress,
    region_filter: Option<fn(&MemoryRegionInformation) -> bool>,
    align: u64,
) -> Result<(GuestAddress, usize), LoadImageError>
where
    F: FileReadWriteAtVolatile + FileGetLen,
{
    if !align.is_power_of_two() {
        return Err(LoadImageError::BadAlignment(align));
    }

    let max_size = max_guest_addr.offset_from(min_guest_addr) & !(align - 1);
    let size = image.get_len().map_err(LoadImageError::GetLen)?;

    if size == 0 {
        return Err(LoadImageError::ZeroSizedImage);
    }

    if size > usize::MAX as u64 || size > max_size {
        return Err(LoadImageError::ImageSizeTooLarge(size));
    }

    // Sort the list of guest memory regions by address so we can iterate over them in reverse order
    // (high to low).
    let mut regions: Vec<_> = guest_mem
        .regions()
        .filter(region_filter.unwrap_or(|_| true))
        .collect();
    regions.sort_unstable_by(|a, b| a.guest_addr.cmp(&b.guest_addr));

    // Find the highest valid address inside a guest memory region that satisfies the requested
    // alignment and min/max address requirements while having enough space for the image.
    let guest_addr = regions
        .into_iter()
        .rev()
        .filter_map(|r| {
            // Highest address within this region.
            let rgn_max_addr = r
                .guest_addr
                .checked_add((r.size as u64).checked_sub(1)?)?
                .min(max_guest_addr);
            // Lowest aligned address within this region.
            let rgn_start_aligned = r.guest_addr.align(align)?;
            // Hypothetical address of the image if loaded at the end of the region.
            let image_addr = rgn_max_addr.checked_sub(size - 1)? & !(align - 1);

            // Would the image fit within the region?
            if image_addr >= rgn_start_aligned {
                Some(image_addr)
            } else {
                None
            }
        })
        .find(|&addr| addr >= min_guest_addr)
        .ok_or(LoadImageError::NoSuitableMemoryRegion)?;

    // This is safe due to the bounds check above.
    let size = size as usize;

    let guest_slice = guest_mem
        .get_slice_at_addr(guest_addr, size)
        .map_err(LoadImageError::GuestMemorySlice)?;
    image
        .read_exact_at_volatile(guest_slice, 0)
        .map_err(LoadImageError::ReadToMemory)?;

    Ok((guest_addr, size))
}

/// SMBIOS table configuration
#[derive(Clone, Debug, Default, Serialize, Deserialize, FromKeyValues, PartialEq, Eq)]
#[serde(deny_unknown_fields, rename_all = "kebab-case")]
pub struct SmbiosOptions {
    /// BIOS vendor name.
    pub bios_vendor: Option<String>,

    /// BIOS version number (free-form string).
    pub bios_version: Option<String>,

    /// System manufacturer name.
    pub manufacturer: Option<String>,

    /// System product name.
    pub product_name: Option<String>,

    /// System serial number (free-form string).
    pub serial_number: Option<String>,

    /// System UUID.
    pub uuid: Option<Uuid>,

    /// Additional OEM strings to add to SMBIOS table.
    #[serde(default)]
    pub oem_strings: Vec<String>,
}

#[cfg(test)]
mod tests {
    use serde_keyvalue::from_key_values;
    use tempfile::tempfile;

    use super::*;

    #[test]
    fn parse_pstore() {
        let res: Pstore = from_key_values("path=/some/path,size=16384").unwrap();
        assert_eq!(
            res,
            Pstore {
                path: "/some/path".into(),
                size: 16384,
            }
        );

        let res = from_key_values::<Pstore>("path=/some/path");
        assert!(res.is_err());

        let res = from_key_values::<Pstore>("size=16384");
        assert!(res.is_err());

        let res = from_key_values::<Pstore>("");
        assert!(res.is_err());
    }

    #[test]
    fn deserialize_cpuset_serde_kv() {
        let res: CpuSet = from_key_values("[0,4,7]").unwrap();
        assert_eq!(res, CpuSet::new(vec![0, 4, 7]));

        let res: CpuSet = from_key_values("[9-12]").unwrap();
        assert_eq!(res, CpuSet::new(vec![9, 10, 11, 12]));

        let res: CpuSet = from_key_values("[0,4,7,9-12,15]").unwrap();
        assert_eq!(res, CpuSet::new(vec![0, 4, 7, 9, 10, 11, 12, 15]));
    }

    #[test]
    fn deserialize_serialize_cpuset_json() {
        let json_str = "[0,4,7]";
        let cpuset = CpuSet::new(vec![0, 4, 7]);
        let res: CpuSet = serde_json::from_str(json_str).unwrap();
        assert_eq!(res, cpuset);
        assert_eq!(serde_json::to_string(&cpuset).unwrap(), json_str);

        let json_str = r#"["9-12"]"#;
        let cpuset = CpuSet::new(vec![9, 10, 11, 12]);
        let res: CpuSet = serde_json::from_str(json_str).unwrap();
        assert_eq!(res, cpuset);
        assert_eq!(serde_json::to_string(&cpuset).unwrap(), json_str);

        let json_str = r#"[0,4,7,"9-12",15]"#;
        let cpuset = CpuSet::new(vec![0, 4, 7, 9, 10, 11, 12, 15]);
        let res: CpuSet = serde_json::from_str(json_str).unwrap();
        assert_eq!(res, cpuset);
        assert_eq!(serde_json::to_string(&cpuset).unwrap(), json_str);
    }

    #[test]
    fn load_image_high_max_4g() {
        let mem = GuestMemory::new(&[
            (GuestAddress(0x0000_0000), 0x4000_0000), // 0x00000000..0x40000000
            (GuestAddress(0x8000_0000), 0x4000_0000), // 0x80000000..0xC0000000
        ])
        .unwrap();

        const TEST_IMAGE_SIZE: u64 = 1234;
        let mut test_image = tempfile().unwrap();
        test_image.set_len(TEST_IMAGE_SIZE).unwrap();

        const TEST_ALIGN: u64 = 0x8000;
        let (addr, size) = load_image_high(
            &mem,
            &mut test_image,
            GuestAddress(0x8000),
            GuestAddress(0xFFFF_FFFF), // max_guest_addr beyond highest guest memory region
            None,
            TEST_ALIGN,
        )
        .unwrap();

        assert_eq!(addr, GuestAddress(0xBFFF_8000));
        assert_eq!(addr.offset() % TEST_ALIGN, 0);
        assert_eq!(size, TEST_IMAGE_SIZE as usize);
    }
}