[PATCH 3/5] KVM: arm/arm64: Require VCPU threads to turn them self off

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To avoid a race between turning VCPUs off and turning them on, make sure
that only the VCPU threat itself turns off the VCPU.  When other threads
want to turn of a VCPU, they now do this via a request.

Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
 arch/arm/include/asm/kvm_host.h   |  2 ++
 arch/arm64/include/asm/kvm_host.h |  2 ++
 virt/kvm/arm/arm.c                |  8 ++++++--
 virt/kvm/arm/psci.c               | 11 ++---------
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 50e89869178a..b1cfae222441 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -49,6 +49,8 @@
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 #define KVM_REQ_VCPU_RESET	KVM_ARCH_REQ(2)
+#define KVM_REQ_VCPU_OFF \
+	KVM_ARCH_REQ_FLAGS(3, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index da3fc7324d68..d43b13421987 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -49,6 +49,8 @@
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 #define KVM_REQ_VCPU_RESET	KVM_ARCH_REQ(2)
+#define KVM_REQ_VCPU_OFF \
+	KVM_ARCH_REQ_FLAGS(3, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 9c486fad3f9f..785076176814 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -404,8 +404,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 
 static void vcpu_power_off(struct kvm_vcpu *vcpu)
 {
-	vcpu->arch.power_off = true;
-	kvm_make_request(KVM_REQ_SLEEP, vcpu);
+	kvm_make_request(KVM_REQ_VCPU_OFF, vcpu);
 	kvm_vcpu_kick(vcpu);
 }
 
@@ -646,6 +645,11 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 		if (kvm_check_request(KVM_REQ_SLEEP, vcpu))
 			vcpu_req_sleep(vcpu);
 
+		if (kvm_check_request(KVM_REQ_VCPU_OFF, vcpu)) {
+			vcpu->arch.power_off = true;
+			vcpu_req_sleep(vcpu);
+		}
+
 		if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
 			kvm_reset_vcpu(vcpu);
 
diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index b9cff1d4b06d..20255319e193 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -97,9 +97,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
 
 static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
 {
-	vcpu->arch.power_off = true;
-	kvm_make_request(KVM_REQ_SLEEP, vcpu);
-	kvm_vcpu_kick(vcpu);
+	kvm_make_request(KVM_REQ_VCPU_OFF, vcpu);
 }
 
 static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
@@ -198,9 +196,6 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 
 static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
 {
-	int i;
-	struct kvm_vcpu *tmp;
-
 	/*
 	 * The KVM ABI specifies that a system event exit may call KVM_RUN
 	 * again and may perform shutdown/reboot at a later time that when the
@@ -210,9 +205,7 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
 	 * after this call is handled and before the VCPUs have been
 	 * re-initialized.
 	 */
-	kvm_for_each_vcpu(i, tmp, vcpu->kvm)
-		tmp->arch.power_off = true;
-	kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
+	kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_VCPU_OFF);
 
 	memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 	vcpu->run->system_event.type = type;
-- 
2.18.0

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