pvKernel 0.0.4 — Hardware Interrupts and Timer

[0.0.4] - 2026-08-01

Added

• A legacy dual 8259 PIC driver (kernel::arch::x86_64::pic): IRQ vector
  remapping to 32-47, per-line masking/unmasking, end-of-interrupt handling
  (including the slave-then-master cascade order), and spurious IRQ7/IRQ15
  detection via the in-service register.
• A PIT channel 0 periodic timer driver (kernel::arch::x86_64::pit),
  configured for approximately 100 Hz, with an atomic tick counter and an
  uptime helper.
• IDT handlers for all 16 remapped IRQ vectors (32-47): a timer handler, two
  spurious-IRQ handlers, and generic handlers for every other line that
  pvKernel keeps masked in this release.
• A boot-time verification that unmasks the timer IRQ, enables maskable
  hardware interrupts, and confirms the tick counter advances before
  continuing.
• A distinction between fatal halting (halt::halt_forever, used for panics
  and fatal CPU exceptions) and an interrupt-enabled idle loop
  (halt::idle_loop), which normal boot now ends in instead of halting
  immediately.
• QEMU isa-debug-exit support (kernel::arch::x86_64::qemu, behind the new
  qemu-test Cargo feature) and a root runner --headless-test flag, so the
  timer and expected-page-fault tests can run deterministically and exit
  with a pass/fail status suitable for CI.
• A qemu-tests CI job running both headless tests on every pull request
  and push to main.
• New documentation:
  docs/architecture/hardware-interrupts.md,
  docs/architecture/timer.md, and
  docs/development/testing.md.

Changed

• The expected-page-fault test (fault-tests feature) now runs after the
  timer verification instead of before it, so a fault-tests build always
  exercises PIC/PIT timer interrupts before its deliberate fault.
• The root runner's window title is now pvKernel 0.0.4.
• The qemu-tests CI job now builds each headless test binary in an
  untimed step before running it, and raises the run timeout to 120
  seconds, since GitHub-hosted runners have no /dev/kvm and fall back to
  slower TCG emulation.

Out of scope for this milestone: APIC, keyboard input, any IRQ line other
than the timer, memory allocation, and scheduling.

Full diff: v0.0.2...v0.0.4