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KVM: X86: Implement PV sched yield hypercall

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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: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li 2019-06-11 20:23:49 +08:00 committed by Paolo Bonzini
parent f85f6e7bc9
commit 715062970f
1 changed files with 21 additions and 0 deletions
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21
arch/x86/kvm/x86.c
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@ -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;