在 qemu 的定义:

target/i386/cpu.c

    [FEAT_KVM] = {
        .type = CPUID_FEATURE_WORD,
        .feat_names = {
            "kvmclock", "kvm-nopiodelay", "kvm-mmu", "kvmclock",
            "kvm-asyncpf", "kvm-steal-time", "kvm-pv-eoi", "kvm-pv-unhalt",
            NULL, "kvm-pv-tlb-flush", "kvm-asyncpf-vmexit", "kvm-pv-ipi",
            "kvm-poll-control", "kvm-pv-sched-yield", "kvm-asyncpf-int", "kvm-msi-ext-dest-id",
            NULL, NULL, NULL, NULL,
            NULL, NULL, NULL, NULL,
            "kvmclock-stable-bit", NULL, NULL, NULL,
            NULL, NULL, NULL, NULL,
        },
        .cpuid = { .eax = KVM_CPUID_FEATURES, .reg = R_EAX, },
        .tcg_features = TCG_KVM_FEATURES,
    },

kvm_emulate_hypercall -> __kvm_emulate_hypercall

KVM_HC_KICK_CPU

好几个 kvm_sched_yield 是看

• directed_yield_attempted
• directed_yield_successful

每一个都是需要仔细看看的:

	case KVM_HC_KICK_CPU:
		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_UNHALT))
			break;

		kvm_pv_kick_cpu_op(vcpu->kvm, a1);
		kvm_sched_yield(vcpu, a1);
		ret = 0;
		break;
#ifdef CONFIG_X86_64
	case KVM_HC_CLOCK_PAIRING:
		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
		break;
#endif
	case KVM_HC_SEND_IPI:
		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SEND_IPI))
			break;

		ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);
		break;
	case KVM_HC_SCHED_YIELD:
		if (!guest_pv_has(vcpu, KVM_FEATURE_PV_SCHED_YIELD))
			break;

		kvm_sched_yield(vcpu, a0);
		ret = 0;
		break;

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