Use irqfd when supported by kernel.

This uses msix mask notifiers: when vector is masked, we poll it from

userspace.  When it is unmasked, we poll it from kernel.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

 hw/virtio-pci.c |   31 +++++++++++++++++++++++++++++--

 1 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c

index c454093..e8e0d82 100644

--- a/hw/virtio-pci.c

+++ b/hw/virtio-pci.c

@@ -404,6 +404,27 @@ static void virtio_pci_guest_notifier_read(void *opaque)

     }

 }

+static int virtio_pci_mask_notifier(PCIDevice *dev, unsigned vector,

+                                    void *opaque, int masked)

+{

+    VirtQueue *vq = opaque;

+    EventNotifier *notifier = virtio_queue_guest_notifier(vq);

+    int r = kvm_set_irqfd(dev->msix_irq_entries[vector].gsi,

+                          event_notifier_get_fd(notifier),

+                          !masked);

+    if (r < 0) {

+        return (r == -ENOSYS) ? 0 : r;

+    }

+    if (masked) {

+        qemu_set_fd_handler(event_notifier_get_fd(notifier),

+                            virtio_pci_guest_notifier_read, NULL, vq);

+    } else {

+        qemu_set_fd_handler(event_notifier_get_fd(notifier),

+                            NULL, NULL, vq);

+    }

+    return 0;

+}

+

 static int virtio_pci_guest_notifier(void *opaque, int n, bool assign)

 {

     VirtIOPCIProxy *proxy = opaque;

@@ -412,11 +433,15 @@ static int virtio_pci_guest_notifier(void *opaque, int n, bool assign)

     if (assign) {

         int r = event_notifier_init(notifier, 0);

-	if (r < 0)

-		return r;

+        if (r < 0)

+            return r;

         qemu_set_fd_handler(event_notifier_get_fd(notifier),

                             virtio_pci_guest_notifier_read, NULL, vq);

+        msix_set_mask_notifier(&proxy->pci_dev,

+			       virtio_queue_vector(proxy->vdev, n), vq);

     } else {

+        msix_set_mask_notifier(&proxy->pci_dev,

+			       virtio_queue_vector(proxy->vdev, n), NULL);

         qemu_set_fd_handler(event_notifier_get_fd(notifier),

                             NULL, NULL, vq);

         event_notifier_cleanup(notifier);

@@ -501,6 +526,8 @@ static void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev,

     proxy->pci_dev.config_write = virtio_write_config;

+    proxy->pci_dev.msix_mask_notifier = virtio_pci_mask_notifier;

+

     size = VIRTIO_PCI_REGION_SIZE(&proxy->pci_dev) + vdev->config_len;

     if (size & (size-1))

         size = 1 << qemu_fls(size);

-- 

1.6.6.144.g5c3af