KVM: PPC: Book3S HV: Manage core host state

Update the core host state in kvmppc_host_rm_ops whenever
the primary thread of the core enters the guest or returns
back.
Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kvm/book3s_hv.c

@@ -2302,6 +2302,46 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master)
 	spin_unlock(&vc->lock);
 }
 
+/*
+ * Clear core from the list of active host cores as we are about to
+ * enter the guest. Only do this if it is the primary thread of the
+ * core (not if a subcore) that is entering the guest.
+ */
+static inline void kvmppc_clear_host_core(int cpu)
+{
+	int core;
+
+	if (!kvmppc_host_rm_ops_hv || cpu_thread_in_core(cpu))
+		return;
+	/*
+	 * Memory barrier can be omitted here as we will do a smp_wmb()
+	 * later in kvmppc_start_thread and we need ensure that state is
+	 * visible to other CPUs only after we enter guest.
+	 */
+	core = cpu >> threads_shift;
+	kvmppc_host_rm_ops_hv->rm_core[core].rm_state.in_host = 0;
+}
+
+/*
+ * Advertise this core as an active host core since we exited the guest
+ * Only need to do this if it is the primary thread of the core that is
+ * exiting.
+ */
+static inline void kvmppc_set_host_core(int cpu)
+{
+	int core;
+
+	if (!kvmppc_host_rm_ops_hv || cpu_thread_in_core(cpu))
+		return;
+
+	/*
+	 * Memory barrier can be omitted here because we do a spin_unlock
+	 * immediately after this which provides the memory barrier.
+	 */
+	core = cpu >> threads_shift;
+	kvmppc_host_rm_ops_hv->rm_core[core].rm_state.in_host = 1;
+}
+
 /*
  * Run a set of guest threads on a physical core.
  * Called with vc->lock held.
@@ -2414,6 +2454,8 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
 		}
 	}
 
+	kvmppc_clear_host_core(pcpu);
+
 	/* Start all the threads */
 	active = 0;
 	for (sub = 0; sub < core_info.n_subcores; ++sub) {
@@ -2510,6 +2552,8 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
 			kvmppc_ipi_thread(pcpu + i);
 	}
 
+	kvmppc_set_host_core(pcpu);
+
 	spin_unlock(&vc->lock);
 
 	/* make sure updates to secondary vcpu structs are visible now */