Add tap(4) read events after rx virtqueue notification.

The recent vmd(8) vionet refactor caused cpu spinning when the
device would be activated by a driver but before virtqueues were
provided. (e.g. booting a ramdisk kernel and not running `ifconfig
vio0 up`)

Defer adding the tap and packet injection read events until after
the first RX queue notification from the driver.

ok mlarkin@

diff --git a/usr.sbin/vmd/vionet.c b/usr.sbin/vmd/vionet.c
index b973577..5f7e146 100644 (file)
--- a/usr.sbin/vmd/vionet.c
+++ b/usr.sbin/vmd/vionet.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vionet.c,v 1.8 2024/01/30 23:01:49 dv Exp $   */
+/*     $OpenBSD: vionet.c,v 1.9 2024/02/03 21:41:35 dv Exp $   */
 
 /*
  * Copyright (c) 2023 Dave Voutila <dv@openbsd.org>
@@ -622,7 +622,12 @@ vionet_notifyq(struct virtio_dev *dev)
        struct vionet_dev *vionet = &dev->vionet;
 
        switch (vionet->cfg.queue_notify) {
-       case TXQ: return vionet_notify_tx(dev);
+       case RXQ:
+               event_add(&ev_tap, NULL);
+               event_add(&ev_inject, NULL);
+               break;
+       case TXQ:
+               return vionet_notify_tx(dev);
        default:
                /*
                 * Catch the unimplemented queue ID 2 (control queue) as
@@ -1027,16 +1032,10 @@ handle_io_write(struct viodev_msg *msg, struct virtio_dev *dev)
                        vionet->vq[TXQ].last_avail = 0;
                        vionet->vq[TXQ].notified_avail = 0;
                        virtio_deassert_pic_irq(dev, msg->vcpu);
+
+                       event_del(&ev_tap);
+                       event_del(&ev_inject);
                }
-               event_del(&ev_tap);
-               event_del(&ev_inject);
-               if (vionet->cfg.device_status
-                   & VIRTIO_CONFIG_DEVICE_STATUS_DRIVER_OK) {
-                       event_add(&ev_tap, NULL);
-                       event_add(&ev_inject, NULL);
-               }
-               break;
-       default:
                break;
        }
        return (intr);