KVM: arm64: Drop vcpu->arch.has_run_once for vcpu->pid

With the transition to kvm_arch_vcpu_run_pid_change() to handle
the "run once" activities, it becomes obvious that has_run_once
is now an exact shadow of vcpu->pid.

Replace vcpu->arch.has_run_once with a new vcpu_has_run_once()
helper that directly checks for vcpu->pid, and get rid of the
now unused field.
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -367,9 +367,6 @@ struct kvm_vcpu_arch {
 	int target;
 	DECLARE_BITMAP(features, KVM_VCPU_MAX_FEATURES);
 
-	/* Detect first run of a vcpu */
-	bool has_run_once;
-
 	/* Virtual SError ESR to restore when HCR_EL2.VSE is set */
 	u64 vsesr_el2;
 
@@ -606,6 +603,8 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
+#define vcpu_has_run_once(vcpu)	!!rcu_access_pointer((vcpu)->pid)
+
 #ifndef __KVM_NVHE_HYPERVISOR__
 #define kvm_call_hyp_nvhe(f, ...)						\
 	({								\

arch/arm64/kvm/arm.c

@@ -351,7 +351,7 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm)))
+	if (vcpu_has_run_once(vcpu) && unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		static_branch_dec(&userspace_irqchip_in_use);
 
 	kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
@@ -609,7 +609,7 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 	if (ret)
 		return ret;
 
-	if (likely(vcpu->arch.has_run_once))
+	if (likely(vcpu_has_run_once(vcpu)))
 		return 0;
 
 	kvm_arm_vcpu_init_debug(vcpu);
@@ -640,8 +640,6 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 		static_branch_inc(&userspace_irqchip_in_use);
 	}
 
-	vcpu->arch.has_run_once = true;
-
 	/*
 	 * Initialize traps for protected VMs.
 	 * NOTE: Move to run in EL2 directly, rather than via a hypercall, once
@@ -1132,7 +1130,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
 	 * need to invalidate the I-cache though, as FWB does *not*
 	 * imply CTR_EL0.DIC.
 	 */
-	if (vcpu->arch.has_run_once) {
+	if (vcpu_has_run_once(vcpu)) {
 		if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
 			stage2_unmap_vm(vcpu->kvm);
 		else

arch/arm64/kvm/vgic/vgic-init.c

@@ -91,7 +91,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
 		return ret;
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (vcpu->arch.has_run_once)
+		if (vcpu_has_run_once(vcpu))
 			goto out_unlock;
 	}
 	ret = 0;