KVM: PPC: Book3S HV P9: Clear vcpu cpu fields before enabling host irqs

On guest entry, vcpu->cpu and vcpu->arch.thread_cpu are set after
disabling host irqs. On guest exit there is a window whre tick time
accounting briefly enables irqs before these fields are cleared.

Move them up to ensure they are cleared before host irqs are run.
This is possibly not a problem, but is more symmetric and makes the
fields less surprising.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220908132545.4085849-1-npiggin@gmail.com

arch/powerpc/kvm/book3s_hv.c

@@ -4629,6 +4629,9 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 
 	set_irq_happened(trap);
 
+	vcpu->cpu = -1;
+	vcpu->arch.thread_cpu = -1;
+
 	context_tracking_guest_exit();
 	if (!vtime_accounting_enabled_this_cpu()) {
 		local_irq_enable();
@@ -4644,9 +4647,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
 	}
 	vtime_account_guest_exit();
 
-	vcpu->cpu = -1;
-	vcpu->arch.thread_cpu = -1;
-
 	powerpc_local_irq_pmu_restore(flags);
 
 	preempt_enable();