vmcs 的很多字段大多数时候不用刷新，所以

arch/x86/kvm/kvm_cache_regs.h

• vcpu_load_eoi_exitmap
  • vmx_load_eoi_exitmap

1. 这里为什么要调整?
2. hyperv 为什么需要有区别? ```c static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu) { if (!kvm_apic_hw_enabled(vcpu->arch.apic)) return;

#ifdef CONFIG_KVM_HYPERV if (to_hv_vcpu(vcpu)) { u64 eoi_exit_bitmap[4];

	bitmap_or((ulong *)eoi_exit_bitmap,
		  vcpu->arch.ioapic_handled_vectors,
		  to_hv_synic(vcpu)->vec_bitmap, 256);
	static_call_cond(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
	return;
} #endif
static_call_cond(kvm_x86_load_eoi_exitmap)(
	vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors); } ``` 这里为什么需要将 ioapic 处理的中断放到 。

表示，如果写 1 ，那么这些位置 eoi 需要 exit ?

复杂啊 : 看看 reference 的位置!

		if (kvm_check_request(KVM_REQ_IOAPIC_EOI_EXIT, vcpu)) {
			BUG_ON(vcpu->arch.pending_ioapic_eoi > 255);
			if (test_bit(vcpu->arch.pending_ioapic_eoi,
				     vcpu->arch.ioapic_handled_vectors)) {
				vcpu->run->exit_reason = KVM_EXIT_IOAPIC_EOI;
				vcpu->run->eoi.vector =
						vcpu->arch.pending_ioapic_eoi;
				r = 0;
				goto out;
			}
		}

为什么要区分 ioapic 的 io ?

static bool kvm_ioapic_handles_vector(struct kvm_lapic *apic, int vector)
{
	return test_bit(vector, apic->vcpu->arch.ioapic_handled_vectors);
}

apic_set_eoi 中为什么需要调用 kvm_ioapic_send_eoi

static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector)
{
	int trigger_mode;

	/* Eoi the ioapic only if the ioapic doesn't own the vector. */
	if (!kvm_ioapic_handles_vector(apic, vector))
		return;

	/* Request a KVM exit to inform the userspace IOAPIC. */
	if (irqchip_split(apic->vcpu->kvm)) {
		apic->vcpu->arch.pending_ioapic_eoi = vector;
		kvm_make_request(KVM_REQ_IOAPIC_EOI_EXIT, apic->vcpu);
		return;
	}

	if (apic_test_vector(vector, apic->regs + APIC_TMR))
		trigger_mode = IOAPIC_LEVEL_TRIG;
	else
		trigger_mode = IOAPIC_EDGE_TRIG;

	kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);
}

如何理解这里的 trap-like exit ?

似乎就是问题的关键了；

难道和 io 路由有关系?

/*
 * this interface assumes a trap-like exit, which has already finished
 * desired side effect including vISR and vPPR update.
 */
void kvm_apic_set_eoi_accelerated(struct kvm_vcpu *vcpu, int vector)
{
	struct kvm_lapic *apic = vcpu->arch.apic;

	trace_kvm_eoi(apic, vector);

	kvm_ioapic_send_eoi(apic, vector);
	kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
}

串口，exit 的时候，为什么是 io instruction

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