LoongArch: KVM: Skip PMU checking on vCPU context switch

PMU hardware about VM is switched on VM exit to host rather than vCPU
context sched off, PMU is checked and restored on return to VM. It is
not necessary to check PMU on vCPU context sched on callback, since the
request is made on the VM exit entry or VM PMU CSR access abort routine
already.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: bibo-mao

arch/loongarch/kvm/vcpu.c

@@ -148,12 +148,6 @@ static void kvm_lose_pmu(struct kvm_vcpu *vcpu)
 	kvm_restore_host_pmu(vcpu);
 }
 
-static void kvm_restore_pmu(struct kvm_vcpu *vcpu)
-{
-	if ((vcpu->arch.aux_inuse & KVM_LARCH_PMU))
-		kvm_make_request(KVM_REQ_PMU, vcpu);
-}
-
 static void kvm_check_pmu(struct kvm_vcpu *vcpu)
 {
 	if (kvm_check_request(KVM_REQ_PMU, vcpu)) {
@@ -304,7 +298,10 @@ static int kvm_pre_enter_guest(struct kvm_vcpu *vcpu)
 		vcpu->arch.aux_inuse &= ~KVM_LARCH_SWCSR_LATEST;
 
 		if (kvm_request_pending(vcpu) || xfer_to_guest_mode_work_pending()) {
-			kvm_lose_pmu(vcpu);
+			if (vcpu->arch.aux_inuse & KVM_LARCH_PMU) {
+				kvm_lose_pmu(vcpu);
+				kvm_make_request(KVM_REQ_PMU, vcpu);
+			}
 			/* make sure the vcpu mode has been written */
 			smp_store_mb(vcpu->mode, OUTSIDE_GUEST_MODE);
 			local_irq_enable();
@@ -1609,9 +1606,6 @@ static int _kvm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	kvm_restore_timer(vcpu);
 	kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
 
-	/* Restore hardware PMU CSRs */
-	kvm_restore_pmu(vcpu);
-
 	/* Don't bother restoring registers multiple times unless necessary */
 	if (vcpu->arch.aux_inuse & KVM_LARCH_HWCSR_USABLE)
 		return 0;