From: Andrew Jones <drjones@redhat.com>
Date: Sun, 4 Jun 2017 14:43:55 +0200
Subject: KVM: arm/arm64: replace pause checks with vcpu request checks
Patch-mainline: v4.13-rc1
Git-commit: 0592c005622582fb4049a2f710d92c3a70f4c79b
References: bsc#1077761

The current use of KVM_REQ_VCPU_EXIT for pause is fine.  Even the
requester clearing the request is OK, as this is the special case
where the sole requesting thread and receiving VCPU are executing
synchronously (see "Clearing Requests" in
Documentation/virtual/kvm/vcpu-requests.rst) However, that's about
to change, so let's ensure only the receiving VCPU clears the
request. Additionally, by guaranteeing KVM_REQ_VCPU_EXIT is always
set when pause is, we can avoid checking pause directly in VCPU RUN.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Acked-by: Alexander Graf <agraf@suse.de>
---
 virt/kvm/arm/arm.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -546,7 +546,6 @@
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		vcpu->arch.pause = false;
-		kvm_clear_request(KVM_REQ_VCPU_EXIT, vcpu);
 		swake_up(kvm_arch_vcpu_wq(vcpu));
 	}
 }
@@ -557,6 +556,11 @@
 
 	swait_event_interruptible(*wq, ((!vcpu->arch.power_off) &&
 				       (!vcpu->arch.pause)));
+
+	if (vcpu->arch.pause) {
+		/* Awaken to handle a signal, request we sleep again later. */
+		kvm_make_request(KVM_REQ_VCPU_EXIT, vcpu);
+	}
 }
 
 static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
@@ -564,6 +568,14 @@
 	return vcpu->arch.target >= 0;
 }
 
+static void check_vcpu_requests(struct kvm_vcpu *vcpu)
+{
+	if (kvm_request_pending(vcpu)) {
+		if (kvm_check_request(KVM_REQ_VCPU_EXIT, vcpu))
+			vcpu_sleep(vcpu);
+	}
+}
+
 /**
  * kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
  * @vcpu:	The VCPU pointer
@@ -609,7 +621,9 @@
 
 		update_vttbr(vcpu->kvm);
 
-		if (vcpu->arch.power_off || vcpu->arch.pause)
+		check_vcpu_requests(vcpu);
+
+		if (vcpu->arch.power_off)
 			vcpu_sleep(vcpu);
 
 		/*
@@ -649,7 +663,7 @@
 
 		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
 		    kvm_request_pending(vcpu) ||
-		    vcpu->arch.power_off || vcpu->arch.pause) {
+		    vcpu->arch.power_off) {
 			vcpu->mode = OUTSIDE_GUEST_MODE;
 			local_irq_enable();
 			kvm_pmu_sync_hwstate(vcpu);