KVM: PPC: Book3S HV: Simplify handling of VCPUs that need a VPA update

Previously, if kvmppc_run_core() was running a VCPU that needed a VPA
update (i.e. one of its 3 virtual processor areas needed to be pinned
in memory so the host real mode code can update it on guest entry and
exit), we would drop the vcore lock and do the update there and then.
Future changes will make it inconvenient to drop the lock, so instead
we now remove it from the list of runnable VCPUs and wake up its
VCPU task.  This will have the effect that the VCPU task will exit
kvmppc_run_vcpu(), go around the do loop in kvmppc_vcpu_run_hv(), and
re-enter kvmppc_run_vcpu(), whereupon it will do the necessary call
to kvmppc_update_vpas() and then rejoin the vcore.

The one complication is that the runner VCPU (whose VCPU task is the
current task) might be one of the ones that gets removed from the
runnable list.  In that case we just return from kvmppc_run_core()
and let the code in kvmppc_run_vcpu() wake up another VCPU task to be
the runner if necessary.

This all means that the VCORE_STARTING state is no longer used, so we
remove it.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/include/asm/kvm_host.h

@@ -306,9 +306,8 @@ struct kvmppc_vcore {
 /* Values for vcore_state */
 #define VCORE_INACTIVE	0
 #define VCORE_SLEEPING	1
-#define VCORE_STARTING	2
-#define VCORE_RUNNING	3
-#define VCORE_EXITING	4
+#define VCORE_RUNNING	2
+#define VCORE_EXITING	3
 
 /*
  * Struct used to manage memory for a virtual processor area

arch/powerpc/kvm/book3s_hv.c

@@ -1863,6 +1863,25 @@ static void kvmppc_start_restoring_l2_cache(const struct kvmppc_vcore *vc)
 	mtspr(SPRN_MPPR, mpp_addr | PPC_MPPR_FETCH_WHOLE_TABLE);
 }
 
+static void prepare_threads(struct kvmppc_vcore *vc)
+{
+	struct kvm_vcpu *vcpu, *vnext;
+
+	list_for_each_entry_safe(vcpu, vnext, &vc->runnable_threads,
+				 arch.run_list) {
+		if (signal_pending(vcpu->arch.run_task))
+			vcpu->arch.ret = -EINTR;
+		else if (vcpu->arch.vpa.update_pending ||
+			 vcpu->arch.slb_shadow.update_pending ||
+			 vcpu->arch.dtl.update_pending)
+			vcpu->arch.ret = RESUME_GUEST;
+		else
+			continue;
+		kvmppc_remove_runnable(vc, vcpu);
+		wake_up(&vcpu->arch.cpu_run);
+	}
+}
+
 /*
  * Run a set of guest threads on a physical core.
  * Called with vc->lock held.
@@ -1872,45 +1891,30 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
 	struct kvm_vcpu *vcpu, *vnext;
 	long ret;
 	u64 now;
-	int i, need_vpa_update;
+	int i;
 	int srcu_idx;
-	struct kvm_vcpu *vcpus_to_update[threads_per_core];
 
-	/* don't start if any threads have a signal pending */
-	need_vpa_update = 0;
-	list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) {
-		if (signal_pending(vcpu->arch.run_task))
-			return;
-		if (vcpu->arch.vpa.update_pending ||
-		    vcpu->arch.slb_shadow.update_pending ||
-		    vcpu->arch.dtl.update_pending)
-			vcpus_to_update[need_vpa_update++] = vcpu;
-	}
+	/*
+	 * Remove from the list any threads that have a signal pending
+	 * or need a VPA update done
+	 */
+	prepare_threads(vc);
+
+	/* if the runner is no longer runnable, let the caller pick a new one */
+	if (vc->runner->arch.state != KVMPPC_VCPU_RUNNABLE)
+		return;
 
 	/*
-	 * Initialize *vc, in particular vc->vcore_state, so we can
-	 * drop the vcore lock if necessary.
+	 * Initialize *vc.
 	 */
 	vc->n_woken = 0;
 	vc->nap_count = 0;
 	vc->entry_exit_count = 0;
 	vc->preempt_tb = TB_NIL;
-	vc->vcore_state = VCORE_STARTING;
 	vc->in_guest = 0;
 	vc->napping_threads = 0;
 	vc->conferring_threads = 0;
 
-	/*
-	 * Updating any of the vpas requires calling kvmppc_pin_guest_page,
-	 * which can't be called with any spinlocks held.
-	 */
-	if (need_vpa_update) {
-		spin_unlock(&vc->lock);
-		for (i = 0; i < need_vpa_update; ++i)
-			kvmppc_update_vpas(vcpus_to_update[i]);
-		spin_lock(&vc->lock);
-	}
-
 	/*
 	 * Make sure we are running on primary threads, and that secondary
 	 * threads are offline.  Also check if the number of threads in this