diff options
| -rw-r--r-- | Documentation/lguest/lguest.c | 8 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 8 |
2 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 655414821edc..7228369d1014 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -895,6 +895,9 @@ static void handle_console_output(int fd, struct virtqueue *vq, bool timeout) } } +/* This is called when we no longer want to hear about Guest changes to a + * virtqueue. This is more efficient in high-traffic cases, but it means we + * have to set a timer to check if any more changes have occurred. */ static void block_vq(struct virtqueue *vq) { struct itimerval itm; @@ -939,6 +942,11 @@ static void handle_net_output(int fd, struct virtqueue *vq, bool timeout) if (!timeout && num) block_vq(vq); + /* We never quite know how long should we wait before we check the + * queue again for more packets. We start at 500 microseconds, and if + * we get fewer packets than last time, we assume we made the timeout + * too small and increase it by 10 microseconds. Otherwise, we drop it + * by one microsecond every time. It seems to work well enough. */ if (timeout) { if (num < last_timeout_num) timeout_usec += 10; diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c index 37344aaee22f..a661bbdae3d6 100644 --- a/drivers/lguest/lguest_device.c +++ b/drivers/lguest/lguest_device.c @@ -98,6 +98,10 @@ static u32 lg_get_features(struct virtio_device *vdev) return features; } +/* The virtio core takes the features the Host offers, and copies the + * ones supported by the driver into the vdev->features array. Once + * that's all sorted out, this routine is called so we can tell the + * Host which features we understand and accept. */ static void lg_finalize_features(struct virtio_device *vdev) { unsigned int i, bits; @@ -108,6 +112,10 @@ static void lg_finalize_features(struct virtio_device *vdev) /* Give virtio_ring a chance to accept features. */ vring_transport_features(vdev); + /* The vdev->feature array is a Linux bitmask: this isn't the + * same as a the simple array of bits used by lguest devices + * for features. So we do this slow, manual conversion which is + * completely general. */ memset(out_features, 0, desc->feature_len); bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8; for (i = 0; i < bits; i++) { |