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author | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 13:39:18 +1100 |
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committer | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 13:59:40 +1100 |
commit | 42b36cc0ce717deeb10030141a43dede763a3ebe (patch) | |
tree | b2dc48b4f16c5dc59461ad24b027d631edda1da4 /drivers/virtio | |
parent | 1200e646ae238afc536be70257290eb33fb6e364 (diff) | |
download | kernel_samsung_crespo-42b36cc0ce717deeb10030141a43dede763a3ebe.zip kernel_samsung_crespo-42b36cc0ce717deeb10030141a43dede763a3ebe.tar.gz kernel_samsung_crespo-42b36cc0ce717deeb10030141a43dede763a3ebe.tar.bz2 |
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/virtio')
-rw-r--r-- | drivers/virtio/virtio_ring.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 0e1bf05..1dc04b6 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; |