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| author | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 03:39:18 +0100 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2007-11-12 03:59:40 +0100 |
| commit | 42b36cc0ce717deeb10030141a43dede763a3ebe (patch) | |
| tree | b2dc48b4f16c5dc59461ad24b027d631edda1da4 /drivers/lguest/lguest_device.c | |
| parent | lguest: Fix lguest virtio-blk backend size computation (diff) | |
| download | linux-42b36cc0ce717deeb10030141a43dede763a3ebe.tar.xz linux-42b36cc0ce717deeb10030141a43dede763a3ebe.zip | |
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/lguest/lguest_device.c')
| -rw-r--r-- | drivers/lguest/lguest_device.c | 3 |
1 files changed, 2 insertions, 1 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; |