ipi.h

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// MIT License
//
// Copyright (c) 2026 Christian Spoo
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

 
#ifndef _MINIOS_IPI_IPI_H_
#define _MINIOS_IPI_IPI_H_
 
#include <miniOS/types.h>
#include <miniOS/arch/x86_64/spinlock.h>
#include <miniOS/arch/x86_64/smp.h>

typedef struct {
    volatile uint32_t ack_count;  /* decremented by each handler */
    uint64_t          virt;       /* virtual address for TLB shootdown */
} ipi_barrier_t;
 
/* One TLB-shootdown barrier PER INITIATOR CPU, indexed by the initiating
 * CPU's cpu_id. A shootdown started by CPU N always uses g_tlb_barriers[N]
 * and is announced on the dedicated vector TLB_SHOOTDOWN_VECTOR_BASE + N
 * (see tlb_shootdown_isr_n() in ipi.c). This means two CPUs initiating a
 * shootdown at the same time never touch the same barrier struct — no lock
 * needed, and no risk of one initiator's ack_count/virt being clobbered by
 * another's concurrent call — with a single shared barrier, two concurrent
 * initiators can flush the wrong address on remote CPUs and drive ack_count
 * below zero (wraps, since it's unsigned), making ipi_barrier_wait() spin
 * forever. */
extern ipi_barrier_t g_tlb_barriers[MAX_CPUS];

static inline void ipi_barrier_ack(ipi_barrier_t *b) {
    __asm__ volatile("lock subl $1, %0" : "+m"(b->ack_count) : : "memory");
}

static inline void ipi_barrier_wait(ipi_barrier_t *b) {
    while (b->ack_count > 0)
        __asm__ volatile("pause" : : : "memory");
}

void ipi_tlb_shootdown(uint64_t virt);

void tlb_shootdown_isr(uint32_t src_cpu);

void ipi_panic_halt(void);

void panic_halt_isr(void *frame);

 
#endif /* _MINIOS_IPI_IPI_H_ */