[PATCH v2 4/4] kvm tools: Use ioeventfd in virtio-rng

[Sasha Levin <levinsasha928@xxxxxxxxx>]

Use ioeventfds to receive notifications of IO events in virtio-rng.
Doing so prevents an exit every time we need to supply randomness
to the guest.

Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 tools/kvm/virtio/rng.c |   27 ++++++++++++++++++++++++++-
 1 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/tools/kvm/virtio/rng.c b/tools/kvm/virtio/rng.c
index 1a3bda3..d5d7795c 100644
--- a/tools/kvm/virtio/rng.c
+++ b/tools/kvm/virtio/rng.c
@@ -10,6 +10,7 @@
 #include "kvm/pci.h"
 #include "kvm/threadpool.h"
 #include "kvm/irq.h"
+#include "kvm/ioeventfd.h"
 
 #include <linux/virtio_ring.h>
 #include <linux/virtio_rng.h>
@@ -154,6 +155,7 @@ static bool virtio_rng_pci_io_out(struct ioport *ioport, struct kvm *kvm, u16 po
 		break;
 	case VIRTIO_PCI_QUEUE_NOTIFY: {
 		u16 queue_index;
+		printf("regular exit");
 		queue_index		= ioport__read16(data);
 		thread_pool__do_job(rdev->jobs[queue_index].job_id);
 		break;
@@ -177,11 +179,19 @@ static struct ioport_operations virtio_rng_io_ops = {
 	.io_out				= virtio_rng_pci_io_out,
 };
 
+static void ioevent_callback(struct kvm *kvm, void *param)
+{
+	struct rng_dev_job *job = param;
+
+	thread_pool__do_job(job->job_id);
+}
+
 void virtio_rng__init(struct kvm *kvm)
 {
-	u8 pin, line, dev;
+	u8 pin, line, dev, i;
 	u16 rdev_base_addr;
 	struct rng_dev *rdev;
+	struct ioevent ioevent;
 
 	rdev = malloc(sizeof(*rdev));
 	if (rdev == NULL)
@@ -213,6 +223,20 @@ void virtio_rng__init(struct kvm *kvm)
 	pci__register(&rdev->pci_hdr, dev);
 
 	list_add_tail(&rdev->list, &rdevs);
+
+	for (i = 0; i < NUM_VIRT_QUEUES; i++) {
+		ioevent = (struct ioevent) {
+			.io_addr		= rdev_base_addr + VIRTIO_PCI_QUEUE_NOTIFY,
+			.io_len			= sizeof(u16),
+			.fn			= ioevent_callback,
+			.fn_ptr			= &rdev->jobs[i],
+			.datamatch		= i,
+			.fn_kvm			= kvm,
+			.fd			= eventfd(0, 0),
+		};
+
+		ioeventfd__add_event(&ioevent);
+	}
 }
 
 void virtio_rng__delete_all(struct kvm *kvm)
@@ -222,6 +246,7 @@ void virtio_rng__delete_all(struct kvm *kvm)
 
 		rdev = list_first_entry(&rdevs, struct rng_dev, list);
 		list_del(&rdev->list);
+		ioeventfd__del_event(rdev->base_addr + VIRTIO_PCI_QUEUE_NOTIFY, 0);
 		free(rdev);
 	}
 }
-- 
1.7.5.rc3

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