[PATCH v4 09/11] KVM: arm/arm64: use vcpu requests for irq injection

[Andrew Jones <drjones@redhat.com>]

Don't use request-less VCPU kicks when injecting IRQs, as a VCPU
kick meant to trigger the interrupt injection could be sent while
the VCPU is outside guest mode, which means no IPI is sent, and
after it has called kvm_vgic_flush_hwstate(), meaning it won't see
the updated GIC state until its next exit some time later for some
other reason.  The receiving VCPU only needs to check this request
in VCPU RUN to handle it.  By checking it, if it's pending, a
memory barrier will be issued that ensures all state is visible.
We still create a vcpu_req_irq_pending() function (which is a nop),
though, in order to allow us to use the standard request checking
pattern.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 arch/arm/include/asm/kvm_host.h   |  1 +
 arch/arm64/include/asm/kvm_host.h |  1 +
 virt/kvm/arm/arm.c                | 12 ++++++++++++
 virt/kvm/arm/vgic/vgic.c          |  9 +++++++--
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index fdd644c01c89..00ad56ee6455 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -46,6 +46,7 @@
 
 #define KVM_REQ_SLEEP \
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 
 u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode);
 int __attribute_const__ kvm_target_cpu(void);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9bd0d1040de9..0c4fd1f46e10 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -43,6 +43,7 @@
 
 #define KVM_REQ_SLEEP \
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 
 int __attribute_const__ kvm_target_cpu(void);
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index ddc833987dfb..73a75ca91e41 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -570,6 +570,15 @@ static void vcpu_req_sleep(struct kvm_vcpu *vcpu)
 	}
 }
 
+static void vcpu_req_irq_pending(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * Nothing to do here. kvm_check_request() already issued a memory
+	 * barrier that pairs with kvm_make_request(), so all hardware state
+	 * we need to flush should now be visible.
+	 */
+}
+
 static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
 {
 	return vcpu->arch.target >= 0;
@@ -580,6 +589,8 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 	if (kvm_request_pending(vcpu)) {
 		if (kvm_check_request(KVM_REQ_SLEEP, vcpu))
 			vcpu_req_sleep(vcpu);
+		if (kvm_check_request(KVM_REQ_IRQ_PENDING, vcpu))
+			vcpu_req_irq_pending(vcpu);
 	}
 }
 
@@ -771,6 +782,7 @@ static int vcpu_interrupt_line(struct kvm_vcpu *vcpu, int number, bool level)
 	 * trigger a world-switch round on the running physical CPU to set the
 	 * virtual IRQ/FIQ fields in the HCR appropriately.
 	 */
+	kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 	kvm_vcpu_kick(vcpu);
 
 	return 0;
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index aea080a2c443..c66feaca2a5d 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -286,8 +286,10 @@ bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq)
 		 * won't see this one until it exits for some other
 		 * reason.
 		 */
-		if (vcpu)
+		if (vcpu) {
+			kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 			kvm_vcpu_kick(vcpu);
+		}
 		return false;
 	}
 
@@ -333,6 +335,7 @@ bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq)
 	spin_unlock(&irq->irq_lock);
 	spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
 
+	kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 	kvm_vcpu_kick(vcpu);
 
 	return true;
@@ -722,8 +725,10 @@ void vgic_kick_vcpus(struct kvm *kvm)
 	 * a good kick...
 	 */
 	kvm_for_each_vcpu(c, vcpu, kvm) {
-		if (kvm_vgic_vcpu_pending_irq(vcpu))
+		if (kvm_vgic_vcpu_pending_irq(vcpu)) {
+			kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
 			kvm_vcpu_kick(vcpu);
+		}
 	}
 }
 
-- 
2.9.3