[PATCH 4/5] KVM: Add the irq handling consumer

[Yunhong Jiang <yunhong.jiang@linux.intel.com>]

Add an irq_bypass consumer to the KVM eventfd, so that when a MSI interrupt
happens and triggerred from VFIO, it can be handled fast.

Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
---
 include/linux/kvm_irqfd.h |  1 +
 virt/kvm/eventfd.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/include/linux/kvm_irqfd.h b/include/linux/kvm_irqfd.h
index 0c1de05098c8..5573d53ccebb 100644
--- a/include/linux/kvm_irqfd.h
+++ b/include/linux/kvm_irqfd.h
@@ -65,6 +65,7 @@ struct kvm_kernel_irqfd {
 	poll_table pt;
 	struct work_struct shutdown;
 	struct irq_bypass_consumer consumer;
+	struct irq_bypass_consumer fastpath;
 	struct irq_bypass_producer *producer;
 };
 
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index c31d43b762db..b20a2d1bbf73 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -144,6 +144,8 @@ irqfd_shutdown(struct work_struct *work)
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 	irq_bypass_unregister_consumer(&irqfd->consumer);
 #endif
+	if (irqfd->fastpath.token)
+		irq_bypass_unregister_consumer(&irqfd->fastpath);
 	eventfd_ctx_put(irqfd->eventfd);
 	kfree(irqfd);
 }
@@ -203,6 +205,14 @@ irqfd_wakeup_pollin(struct kvm_kernel_irqfd *irqfd)
 }
 
 static int
+kvm_fastpath_irq(void *arg)
+{
+	struct kvm_kernel_irqfd *irqfd = arg;
+
+	return irqfd_wakeup_pollin(irqfd);
+}
+
+static int
 irqfd_wakeup_pollup(struct kvm_kernel_irqfd *irqfd)
 {
 	struct kvm *kvm = irqfd->kvm;
@@ -296,6 +306,34 @@ int  __attribute__((weak)) kvm_arch_update_irqfd_routing(
 }
 #endif
 
+static int kvm_fastpath_stub(struct irq_bypass_consumer *stub,
+			     struct irq_bypass_producer *stub1)
+{
+	return 0;
+}
+
+static void kvm_fastpath_stub1(struct irq_bypass_consumer *stub,
+			     struct irq_bypass_producer *stub1)
+{
+}
+
+static int setup_fastpath_consumer(struct kvm_kernel_irqfd *irqfd)
+{
+	int ret;
+
+	irqfd->fastpath.token = (void *)irqfd->eventfd;
+	irqfd->fastpath.add_producer = kvm_fastpath_stub;
+	irqfd->fastpath.del_producer = kvm_fastpath_stub1;
+	irqfd->fastpath.handle_irq = kvm_fastpath_irq;
+	irqfd->fastpath.irq_context = irqfd;
+	ret = irq_bypass_register_consumer(&irqfd->fastpath);
+
+	if (ret)
+		/* A special tag to indicate consumer not working */
+		irqfd->fastpath.token = (void *)0;
+	return ret;
+}
+
 static int
 kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 {
@@ -435,6 +473,10 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 				irqfd->consumer.token, ret);
 #endif
 
+	if (setup_fastpath_consumer(irqfd))
+		pr_info("irq bypass fastpath consumer (toke %p) registration fails: %d\n",
+				irqfd->eventfd, ret);
+
 	return 0;
 
 fail:
-- 
1.8.3.1