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Commit 71506297 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
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KVM: X86: Implement PV sched yield hypercall 



The target vCPUs are in runnable state after vcpu_kick and suitable
as a yield target. This patch implements the sched yield hypercall.

17% performance increasement of ebizzy benchmark can be observed in an
over-subscribe environment. (w/ kvm-pv-tlb disabled, testing TLB flush
call-function IPI-many since call-function is not easy to be trigged
by userspace workload).

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f85f6e7b

arch/x86/kvm/x86.c

+21 −0
Original line number Diff line number Diff line
@@ -7193,6 +7193,23 @@ void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu) 
	kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);

}



static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)

{

	struct kvm_vcpu *target = NULL;

	struct kvm_apic_map *map;



	rcu_read_lock();

	map = rcu_dereference(kvm->arch.apic_map);



	if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])

		target = map->phys_map[dest_id]->vcpu;



	rcu_read_unlock();



	if (target)

		kvm_vcpu_yield_to(target);

}



int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)

{

	unsigned long nr, a0, a1, a2, a3, ret;
@@ -7239,6 +7256,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) 
	case KVM_HC_SEND_IPI:

		ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);

		break;

	case KVM_HC_SCHED_YIELD:

		kvm_sched_yield(vcpu->kvm, a0);

		ret = 0;

		break;

	default:

		ret = -KVM_ENOSYS;

		break;