KVM: PPC: exit halt polling on need_resched()

This is inspired by commit 262de410 (kvm: exit halt polling on
need_resched() as well). Due to PPC implements an arch specific halt
polling logic, we have to the need_resched() check there as well. This
patch adds a helper function that can be shared between book3s and generic
halt-polling loops.
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Venkatesh Srinivas <venkateshs@chromium.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Venkatesh Srinivas <venkateshs@chromium.org>
Cc: Jim Mattson <jmattson@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1621339235-11131-1-git-send-email-wanpengli@tencent.com>
[Make the function inline. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/powerpc/kvm/book3s_hv.c

@@ -3936,7 +3936,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
 				break;
 			}
 			cur = ktime_get();
-		} while (single_task_running() && ktime_before(cur, stop));
+		} while (kvm_vcpu_can_poll(cur, stop));
 
 		spin_lock(&vc->lock);
 		vc->vcore_state = VCORE_INACTIVE;

include/linux/kvm_host.h

@@ -10,6 +10,7 @@
 #include <linux/spinlock.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
+#include <linux/sched/stat.h>
 #include <linux/bug.h>
 #include <linux/minmax.h>
 #include <linux/mm.h>
@@ -265,6 +266,11 @@ static inline bool kvm_vcpu_mapped(struct kvm_host_map *map)
 	return !!map->hva;
 }
 
+static inline bool kvm_vcpu_can_poll(ktime_t cur, ktime_t stop)
+{
+	return single_task_running() && !need_resched() && ktime_before(cur, stop);
+}
+
 /*
  * Sometimes a large or cross-page mmio needs to be broken up into separate
  * exits for userspace servicing.

virt/kvm/kvm_main.c

@@ -2973,8 +2973,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 				goto out;
 			}
 			poll_end = cur = ktime_get();
-		} while (single_task_running() && !need_resched() &&
-			 ktime_before(cur, stop));
+		} while (kvm_vcpu_can_poll(cur, stop));
 	}
 
 	prepare_to_rcuwait(&vcpu->wait);