lguest: publish last_avail_idx. Set the VIRTIO_RING_F_PUBLISH_INDICES feature on all devices, and use the last_avail within the vring rather than storing our own. Signed-off-by: Rusty Russell --- Documentation/lguest/lguest.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff -r f235cacdf13d Documentation/lguest/lguest.c --- a/Documentation/lguest/lguest.c Fri May 02 09:39:33 2008 +1000 +++ b/Documentation/lguest/lguest.c Fri May 02 18:32:12 2008 +1000 @@ -151,9 +151,6 @@ struct virtqueue /* The actual ring of buffers. */ struct vring vring; - - /* Last available index we saw. */ - u16 last_avail_idx; /* The routine to call when the Guest pings us. */ void (*handle_output)(int fd, struct virtqueue *me); @@ -658,19 +655,22 @@ static unsigned get_vq_desc(struct virtq unsigned int *out_num, unsigned int *in_num) { unsigned int i, head; + u16 last_avail; /* Check it isn't doing very strange things with descriptor numbers. */ - if ((u16)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num) + last_avail = vring_last_avail(&vq->vring); + if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num) errx(1, "Guest moved used index from %u to %u", - vq->last_avail_idx, vq->vring.avail->idx); + last_avail, vq->vring.avail->idx); /* If there's nothing new since last we looked, return invalid. */ - if (vq->vring.avail->idx == vq->last_avail_idx) + if (vq->vring.avail->idx == last_avail) return vq->vring.num; /* Grab the next descriptor number they're advertising, and increment * the index we've seen. */ - head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num]; + head = vq->vring.avail->ring[last_avail % vq->vring.num]; + vring_last_avail(&vq->vring)++; /* If their number is silly, that's a fatal mistake. */ if (head >= vq->vring.num) @@ -945,7 +945,7 @@ static void update_device_status(struct for (vq = dev->vq; vq; vq = vq->next) { memset(vq->vring.desc, 0, vring_size(vq->config.num, getpagesize())); - vq->last_avail_idx = 0; + vring_last_avail(&vq->vring) = 0; } } else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) { warnx("Device %s configuration FAILED", dev->name); @@ -1105,7 +1105,6 @@ static void add_virtqueue(struct device /* Initialize the virtqueue */ vq->next = NULL; - vq->last_avail_idx = 0; vq->dev = dev; /* Initialize the configuration. */ @@ -1161,6 +1160,10 @@ static void add_feature(struct device *d * how we use it. */ static void set_config(struct device *dev, unsigned len, const void *conf) { + /* We always set the VIRTIO_RING_F_PUBLISH_INDICES feature + * bit, so now is a good time to do that. */ + add_feature(dev, VIRTIO_RING_F_PUBLISH_INDICES); + /* Check we haven't overflowed our single page. */ if (device_config(dev) + len > devices.descpage + getpagesize()) errx(1, "Too many devices"); @@ -1235,6 +1238,8 @@ static void setup_console(void) add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd); add_virtqueue(dev, VIRTQUEUE_NUM, handle_console_output); + /* Every device should set this bit. */ + add_feature(dev, VIRTIO_RING_F_PUBLISH_INDICES); verbose("device %u: console\n", devices.device_num++); } /*:*/