KVM: Rename kvm_vcpu_block() => kvm_vcpu_halt()

Rename kvm_vcpu_block() to kvm_vcpu_halt() in preparation for splitting
the actual "block" sequences into a separate helper (to be named
kvm_vcpu_block()).  x86 will use the standalone block-only path to handle
non-halt cases where the vCPU is not runnable.

Rename block_ns to halt_ns to match the new function name.

No functional change intended.

Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm64/kvm/arch_timer.c

@@ -467,7 +467,7 @@ out:
 }
 
 /*
- * Schedule the background timer before calling kvm_vcpu_block, so that this
+ * Schedule the background timer before calling kvm_vcpu_halt, so that this
  * thread is removed from its waitqueue and made runnable when there's a timer
  * interrupt to handle.
  */

arch/arm64/kvm/arm.c

@@ -681,7 +681,7 @@ void kvm_vcpu_wfi(struct kvm_vcpu *vcpu)
 	vgic_v4_put(vcpu, true);
 	preempt_enable();
 
-	kvm_vcpu_block(vcpu);
+	kvm_vcpu_halt(vcpu);
 	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 
 	preempt_disable();

arch/arm64/kvm/handle_exit.c

@@ -82,7 +82,7 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
  *
  * WFE: Yield the CPU and come back to this vcpu when the scheduler
  * decides to.
- * WFI: Simply call kvm_vcpu_block(), which will halt execution of
+ * WFI: Simply call kvm_vcpu_halt(), which will halt execution of
  * world-switches and schedule other host processes until there is an
  * incoming IRQ or FIQ to the VM.
  */

arch/arm64/kvm/psci.c

@@ -46,7 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
 	 * specification (ARM DEN 0022A). This means all suspend states
 	 * for KVM will preserve the register state.
 	 */
-	kvm_vcpu_block(vcpu);
+	kvm_vcpu_halt(vcpu);
 	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 
 	return PSCI_RET_SUCCESS;

arch/mips/kvm/emulate.c

@@ -952,7 +952,7 @@ enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
 	if (!vcpu->arch.pending_exceptions) {
 		kvm_vz_lose_htimer(vcpu);
 		vcpu->arch.wait = 1;
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 
 		/*
 		 * We we are runnable, then definitely go off to user space to

arch/powerpc/kvm/book3s_pr.c

@@ -492,7 +492,7 @@ static void kvmppc_set_msr_pr(struct kvm_vcpu *vcpu, u64 msr)
 
 	if (msr & MSR_POW) {
 		if (!vcpu->arch.pending_exceptions) {
-			kvm_vcpu_block(vcpu);
+			kvm_vcpu_halt(vcpu);
 			kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 			vcpu->stat.generic.halt_wakeup++;
 

arch/powerpc/kvm/book3s_pr_papr.c

@@ -376,7 +376,7 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
 		return kvmppc_h_pr_stuff_tce(vcpu);
 	case H_CEDE:
 		kvmppc_set_msr_fast(vcpu, kvmppc_get_msr(vcpu) | MSR_EE);
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 		vcpu->stat.generic.halt_wakeup++;
 		return EMULATE_DONE;

arch/powerpc/kvm/booke.c

@@ -718,7 +718,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
 
 	if (vcpu->arch.shared->msr & MSR_WE) {
 		local_irq_enable();
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 		hard_irq_disable();
 

arch/powerpc/kvm/powerpc.c

@@ -236,7 +236,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 		break;
 	case EV_HCALL_TOKEN(EV_IDLE):
 		r = EV_SUCCESS;
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 		break;
 	default:

arch/riscv/kvm/vcpu_exit.c

@@ -146,7 +146,7 @@ static int system_opcode_insn(struct kvm_vcpu *vcpu,
 		vcpu->stat.wfi_exit_stat++;
 		if (!kvm_arch_vcpu_runnable(vcpu)) {
 			srcu_read_unlock(&vcpu->kvm->srcu, vcpu->arch.srcu_idx);
-			kvm_vcpu_block(vcpu);
+			kvm_vcpu_halt(vcpu);
 			vcpu->arch.srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
 			kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 		}

arch/s390/kvm/interrupt.c

@@ -1335,7 +1335,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
 	VCPU_EVENT(vcpu, 4, "enabled wait: %llu ns", sltime);
 no_timer:
 	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
-	kvm_vcpu_block(vcpu);
+	kvm_vcpu_halt(vcpu);
 	vcpu->valid_wakeup = false;
 	__unset_cpu_idle(vcpu);
 	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);

arch/x86/kvm/x86.c

@@ -8727,6 +8727,13 @@ void kvm_arch_exit(void)
 
 static int __kvm_emulate_halt(struct kvm_vcpu *vcpu, int state, int reason)
 {
+	/*
+	 * The vCPU has halted, e.g. executed HLT.  Update the run state if the
+	 * local APIC is in-kernel, the run loop will detect the non-runnable
+	 * state and halt the vCPU.  Exit to userspace if the local APIC is
+	 * managed by userspace, in which case userspace is responsible for
+	 * handling wake events.
+	 */
 	++vcpu->stat.halt_exits;
 	if (lapic_in_kernel(vcpu)) {
 		vcpu->arch.mp_state = state;
@@ -9999,7 +10006,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
 	if (!kvm_arch_vcpu_runnable(vcpu) &&
 	    (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) {
 		srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 		vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
 
 		if (kvm_x86_ops.post_block)
@@ -10196,7 +10203,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 			r = -EINTR;
 			goto out;
 		}
-		kvm_vcpu_block(vcpu);
+		kvm_vcpu_halt(vcpu);
 		if (kvm_apic_accept_events(vcpu) < 0) {
 			r = 0;
 			goto out;

include/linux/kvm_host.h

@@ -1102,7 +1102,7 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);
 void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
 
-void kvm_vcpu_block(struct kvm_vcpu *vcpu);
+void kvm_vcpu_halt(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);

virt/kvm/kvm_main.c

@@ -3294,17 +3294,14 @@ static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
 	}
 }
 
-/*
- * The vCPU has executed a HLT instruction with in-kernel mode enabled.
- */
-void kvm_vcpu_block(struct kvm_vcpu *vcpu)
+void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
 {
 	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
 	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
 	bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns;
 	ktime_t start, cur, poll_end;
 	bool waited = false;
-	u64 block_ns;
+	u64 halt_ns;
 
 	start = cur = poll_end = ktime_get();
 	if (do_halt_poll) {
@@ -3346,7 +3343,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 				ktime_to_ns(cur) - ktime_to_ns(poll_end));
 	}
 out:
-	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
+	/* The total time the vCPU was "halted", including polling time. */
+	halt_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
 	/*
 	 * Note, halt-polling is considered successful so long as the vCPU was
@@ -3360,24 +3358,24 @@ out:
 		if (!vcpu_valid_wakeup(vcpu)) {
 			shrink_halt_poll_ns(vcpu);
 		} else if (vcpu->kvm->max_halt_poll_ns) {
-			if (block_ns <= vcpu->halt_poll_ns)
+			if (halt_ns <= vcpu->halt_poll_ns)
 				;
 			/* we had a long block, shrink polling */
 			else if (vcpu->halt_poll_ns &&
-					block_ns > vcpu->kvm->max_halt_poll_ns)
+				 halt_ns > vcpu->kvm->max_halt_poll_ns)
 				shrink_halt_poll_ns(vcpu);
 			/* we had a short halt and our poll time is too small */
 			else if (vcpu->halt_poll_ns < vcpu->kvm->max_halt_poll_ns &&
-					block_ns < vcpu->kvm->max_halt_poll_ns)
+				 halt_ns < vcpu->kvm->max_halt_poll_ns)
 				grow_halt_poll_ns(vcpu);
 		} else {
 			vcpu->halt_poll_ns = 0;
 		}
 	}
 
-	trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
+	trace_kvm_vcpu_wakeup(halt_ns, waited, vcpu_valid_wakeup(vcpu));
 }
-EXPORT_SYMBOL_GPL(kvm_vcpu_block);
+EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
 
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
 {