Module smp 

SMP (Symmetric Multi-Processing) boot for x86_64.

Boots Application Processors (APs) using the legacy INIT+SIPI sequence. Inspired by Redox-OS’s approach: a minimal trampoline does the 16→64 bit mode switch, then jumps directly to smp_main in Rust.

Data layout after the trampoline code (written by BSP, read by AP): offset +0: PML4 physical address (CR3) offset +8: kernel stack top virtual address (RSP)

Synchronization: AP increments BOOTED_CORES after finishing per-CPU init. BSP spins until all expected APs are online.

Constants

TRAMPOLINE_PHYS_ADDR

Physical address where the SMP trampoline is copied.

Statics

AP_SCHED_GATE_OPEN 🔒

Gate used by BSP to release APs into scheduler/timer start.

BARRIER_TARGET 🔒

Target count for the rendezvous barrier (set by BSP before barrier).

BOOTED_CORES 🔒

Number of booted cores (starts at 1 for BSP).

SYNC_BARRIER 🔒

Counter for synchronization barriers.

Functions

broadcast_panic_halt

Broadcast a halt command to all other CPUs.

copy_trampoline 🔒

Copy the trampoline to physical address 0x8000 and write the data area.

cpu_count

Return the number of online CPUs.

ensure_identity_mapping 🔒

Identity-map the trampoline physical pages so the AP can execute the trampoline code in real mode / protected mode before paging is enabled.

init

Boot Application Processors.

open_ap_scheduler_gate

Allow APs to start their local timer and enter the scheduler.

rendezvous_barrier 🔒

Wait at a synchronization barrier until all expected CPUs arrive.

send_init_sipi 🔒

Send INIT + SIPI×2 to an AP per Intel SDM Volume 3, Section 10.6.7.1.

send_ipi 🔒

Send an IPI and wait for delivery.

smp_main

First Rust function executed on APs after the trampoline.

smp_trampoline 🔒 ^⚠

smp_trampoline_end 🔒 ^⚠

udelay 🔒

Busy-wait for the given number of microseconds (very rough).

wait_delivery 🔒

Wait for ICR delivery to complete.