diff options
| author | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 05:39:18 +0300 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 05:59:40 +0300 |
| commit | 42b36cc0ce717deeb10030141a43dede763a3ebe (patch) | |
| tree | b2dc48b4f16c5dc59461ad24b027d631edda1da4 /drivers | |
| parent | 1200e646ae238afc536be70257290eb33fb6e364 (diff) | |
| download | linux-42b36cc0ce717deeb10030141a43dede763a3ebe.tar.xz | |
virtio: Force use of power-of-two for descriptor ring sizes
The virtio descriptor rings of size N-1 were nicely set up to be
aligned to an N-byte boundary. But as Anthony Liguori points out, the
free-running indices used by virtio require that the sizes be a power
of 2, otherwise we get problems on wrap (demonstrated with lguest).
So we replace the clever "2^n-1" scheme with a simple "align to page
boundary" scheme: this means that all virtio rings take at least two
pages, but it's safer than guessing cache alignment.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/lguest/lguest_device.c | 3 | ||||
| -rw-r--r-- | drivers/virtio/virtio_ring.c | 8 |
2 files changed, 9 insertions, 2 deletions
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c index 8904f72f97c6..66f38722253a 100644 --- a/drivers/lguest/lguest_device.c +++ b/drivers/lguest/lguest_device.c @@ -200,7 +200,8 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, /* Figure out how many pages the ring will take, and map that memory */ lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT, - DIV_ROUND_UP(vring_size(lvq->config.num), + DIV_ROUND_UP(vring_size(lvq->config.num, + PAGE_SIZE), PAGE_SIZE)); if (!lvq->pages) { err = -ENOMEM; diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 0e1bf053d8cd..1dc04b6684e6 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -277,11 +277,17 @@ struct virtqueue *vring_new_virtqueue(unsigned int num, struct vring_virtqueue *vq; unsigned int i; + /* We assume num is a power of 2. */ + if (num & (num - 1)) { + dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); + return NULL; + } + vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); if (!vq) return NULL; - vring_init(&vq->vring, num, pages); + vring_init(&vq->vring, num, pages, PAGE_SIZE); vq->vq.callback = callback; vq->vq.vdev = vdev; vq->vq.vq_ops = &vring_vq_ops; |