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

Yunhong Jiang
2015-12-03T18:38:00Z

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