feat: Introduce interrupt remapping for vfio

[junyu0312]

Summary by CodeRabbit

Release Notes

• New Features

  • Added interrupt file descriptor routing for improved VM interrupt handling
  • Added VFIO PCI device interrupt support (INTx, MSI, MSI-X capabilities)
  • Enhanced MSI capability structures with 64-bit and per-vector masking variants
  • Added PCI configuration space utilities for improved device management

• Refactoring

  • Replaced raw PCI register constants with strongly-typed enums for improved type safety

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR wires VFIO PCI interrupt capability setup end-to-end. It adds set_irqfd/set_irqfd_with_resample to HypervisorVm (with KVM implementation), redesigns MSI/MSI-X PCI capability structs and introduces PciCommand bitflags, defines VfioInterruptManager with INTx/MSI/MSI-X data structures, implements setup_interrupt_capability in VfioPciDevice, and propagates HypervisorVm through DeviceManagerBuilder.

Changes

VFIO PCI interrupt capability setup

Layer / File(s)	Summary
vmm-sys-util dependency and irqfd trait/KVM impl Cargo.toml, crates/vm-core/Cargo.toml, crates/vm-vfio/Cargo.toml, crates/vm-core/src/virtualization/vm.rs, crates/vm-core/src/virtualization/kvm/vm.rs	Adds vmm-sys-util = "0.15.0" to the workspace and as a Linux-only dep in vm-core/vm-vfio, then extends HypervisorVm with Linux-only set_irqfd/set_irqfd_with_resample methods and implements them on KvmVm using vm_fd.register_irqfd*.
PciCommand bitflags, PciConfigurationSpace, and MSI/MSI-X capability structs crates/vm-pci/Cargo.toml, crates/vm-pci/src/types/configuration_space/command.rs, crates/vm-pci/src/types/configuration_space/header.rs, crates/vm-pci/src/types/configuration_space/status.rs, crates/vm-pci/src/types/configuration_space.rs, crates/vm-pci/src/device/capability/msi.rs, crates/vm-pci/src/device/capability/msix.rs, crates/vm-pci/src/device/interrupt/legacy.rs	Introduces PciCommand as a bitflags type replacing removed raw constants, adds PciConfigurationSpace with find_cap, rewrites PciMsiCap and adds PciMsiCap64/PciMsiCapMask/PciMsiCap64Mask variants with From<...> for StandardCapability impls, adds MSI-X bitmask constants, and derives FromRepr on InterruptPin.
PciCommand adoption in type0, virtio, and VFIO function crates/vm-pci/src/types/function/type0.rs, crates/vm-virtio/src/transport/pci/interrupt.rs, crates/vm-virtio/src/transport/pci/isr_handler.rs, crates/vm-vfio/src/vfio_pci/function.rs	Updates write_command and ISR read/notify paths in vm-pci, vm-virtio, and vm-vfio to use PciCommand::from_bits_retain(...).contains(...) and PciStatus::Interrupt as u16 instead of raw u16 bitmask comparisons and removed constants.
VFIO interrupt data structures and VfioDevice IRQ helpers crates/vm-vfio/src/vfio_pci.rs, crates/vm-vfio/src/vfio_pci/interrupt.rs, crates/vm-vfio/src/vfio_pci/interrupt/intx.rs, crates/vm-vfio/src/vfio_pci/interrupt/msi.rs, crates/vm-vfio/src/vfio_pci/interrupt/msix.rs, crates/vm-vfio/src/vfio/device.rs	Adds VfioInterruptManager with Option<VfioIntx/VfioMsi/VfioMsix> fields, their backing structs, and VfioDevice pub(crate) methods for querying and enabling INTx/MSI/MSI-X IRQs via VFIO ioctl wrappers.
VfioPciDevice interrupt capability setup and constructor crates/vm-vfio/src/vfio_pci/device.rs, crates/vm-vfio/src/error.rs, crates/vm-vfio/src/lib.rs	Adds setup_interrupt_capability to parse MSI/MSI-X/INTx from raw PCI config via PciConfigurationSpace::find_cap, allocate emulated capabilities, validate VFIO IRQ info, and register INTx eventfds via HypervisorVm::set_irqfd_with_resample. Updates VfioPciDevice::new to accept vm, normalize the emulated header, and store interrupt_manager.
HypervisorVm propagation through DeviceManagerBuilder crates/vm-vmm/src/vm/device_builder.rs, crates/vm-vmm/src/vm/device_builder/vfio.rs, crates/vm-vmm/src/vm/config.rs, crates/vm-vmm/src/vm/snapshot.rs	Adds vm: &'a dyn HypervisorVm to DeviceManagerBuilder, threads it through init_vfio_device to VfioPciDevice::new, and updates call sites in Vm::from_config and Vm::from_snapshot.

Sequence Diagram

sequenceDiagram
  participant Vm as Vm::from_config
  participant DMB as DeviceManagerBuilder
  participant VfioPciDevice
  participant SIC as setup_interrupt_capability
  participant PciCfgSpc as PciConfigurationSpace
  participant VfioDevice
  participant HypervisorVm as KvmVm (HypervisorVm)

  Vm->>DMB: new(vm_instance.as_ref(), ...)
  DMB->>VfioPciDevice: new(name, vm, vfio_device, irq_allocator)
  VfioPciDevice->>PciCfgSpc: from_buf(raw_pci_config)
  VfioPciDevice->>SIC: setup_interrupt_capability(vm, vfio_device, config)
  SIC->>PciCfgSpc: find_cap(MSI-X)
  SIC->>PciCfgSpc: find_cap(MSI)
  SIC->>VfioDevice: get_msix_irq_info() / get_msi_irq_info()
  SIC->>PciCfgSpc: find_cap(INTx)
  SIC->>VfioDevice: get_intx_irq_info() / enable_intx(active_fd)
  SIC->>VfioDevice: set_intx_resample_fd(resample_fd)
  SIC->>HypervisorVm: set_irqfd_with_resample(active_fd, resample_fd, gsi)
  HypervisorVm-->>SIC: Ok(())
  SIC-->>VfioPciDevice: VfioInterruptManager { intx, msi, msix }
  VfioPciDevice-->>DMB: VfioPciDevice { name, function, interrupt_manager }

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• junyu0312/rust-vm#73: Introduced StandardCapability/ExtendedCapability and changed ConfigurationSpace capability allocation APIs in the same vm-pci modules that this PR extends with MSI From<...> for StandardCapability impls and PciConfigurationSpace.
• junyu0312/rust-vm#161: Also modifies VfioPciDevice::new constructor signature in crates/vm-vfio/src/vfio_pci/device.rs, directly overlapping with this PR's addition of the vm: &dyn HypervisorVm parameter and interrupt setup.
• junyu0312/rust-vm#176: Both PRs modify VfioPciFunction::write_command in crates/vm-vfio/src/vfio_pci/function.rs at the PIO/MMIO router update logic.

Poem

🐇 Hoppity-hop through the IRQ lane,
EventFds bounce like drops of rain.
MSI, MSI-X, and INTx too—
All wired with bitflags, shiny and new!
The rabbit registers every gsi,
And resamples the world with a cheerful sigh. 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: Introduce interrupt remapping for vfio' accurately summarizes the main objective of the pull request, which is to introduce interrupt remapping capabilities for VFIO devices.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch vfio

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