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Commit f2b56a76 authored by Jintack Lim's avatar Jintack Lim Committed by android-build-merger
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KVM: arm/arm64: Let vcpu thread modify its own active state

am: d29e6215

Change-Id: Ie850ee7a02d3d66511b57b48eee7d80e03f630ad
parents 8b551ea6 d29e6215
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+24 −8
Original line number Diff line number Diff line
@@ -187,21 +187,37 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
				    bool new_active_state)
{
	struct kvm_vcpu *requester_vcpu;
	spin_lock(&irq->irq_lock);

	/*
	 * The vcpu parameter here can mean multiple things depending on how
	 * this function is called; when handling a trap from the kernel it
	 * depends on the GIC version, and these functions are also called as
	 * part of save/restore from userspace.
	 *
	 * Therefore, we have to figure out the requester in a reliable way.
	 *
	 * When accessing VGIC state from user space, the requester_vcpu is
	 * NULL, which is fine, because we guarantee that no VCPUs are running
	 * when accessing VGIC state from user space so irq->vcpu->cpu is
	 * always -1.
	 */
	requester_vcpu = kvm_arm_get_running_vcpu();

	/*
	 * If this virtual IRQ was written into a list register, we
	 * have to make sure the CPU that runs the VCPU thread has
	 * synced back LR state to the struct vgic_irq.  We can only
	 * know this for sure, when either this irq is not assigned to
	 * anyone's AP list anymore, or the VCPU thread is not
	 * running on any CPUs.
	 * synced back the LR state to the struct vgic_irq.
	 *
	 * In the opposite case, we know the VCPU thread may be on its
	 * way back from the guest and still has to sync back this
	 * IRQ, so we release and re-acquire the spin_lock to let the
	 * other thread sync back the IRQ.
	 * As long as the conditions below are true, we know the VCPU thread
	 * may be on its way back from the guest (we kicked the VCPU thread in
	 * vgic_change_active_prepare)  and still has to sync back this IRQ,
	 * so we release and re-acquire the spin_lock to let the other thread
	 * sync back the IRQ.
	 */
	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
	       irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
	       irq->vcpu->cpu != -1) /* VCPU thread is running */
		cond_resched_lock(&irq->irq_lock);