On Fri, 13 Mar 2015 20:42:03 +1100
Alexey Kardashevskiy <a...@ozlabs.ru> wrote:
> The value returned by virtio_vring_size() is used to allocate memory
> for vring. The used descriptor list (array of vring_used_elem) is
> counted by the header - vring_used struct - is not.
>
> This fixes virtio_vring_size() to return the correct size.
> At the moment rings are quite small (256) and allocated with
> 4096 alignment, this is why we have not been having issues with
> this so far.
>
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
> Changes:
> v2:
> * remove magic numbers
> ---
> lib/libvirtio/virtio.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c
> index b010796..f9c00a6 100644
> --- a/lib/libvirtio/virtio.c
> +++ b/lib/libvirtio/virtio.c
> @@ -32,8 +32,10 @@
> */
> unsigned long virtio_vring_size(unsigned int qsize)
> {
> - return VQ_ALIGN(sizeof(struct vring_desc) * qsize + 2 * (2 + qsize))
> - + VQ_ALIGN(sizeof(struct vring_used_elem) * qsize);
> + return VQ_ALIGN(sizeof(struct vring_desc) * qsize +
> + sizeof(struct vring_avail) + sizeof(uint16_t) *
> qsize) +
> + VQ_ALIGN(sizeof(struct vring_used) +
> + sizeof(struct vring_used_elem) * qsize);
> }
Reviewed-by: Thomas Huth <th...@linux.vnet.ibm.com>
That should be at least ok for the current status that we support in
SLOF. I think I might have written the original version of that
function with a very old version of the virtio spec (v0.8.10), when
ther was no "used_event" event field in the struct vring_avail defined
yet.
But if SLOF ever supports VIRTIO_F_EVENT_IDX, we've got to keep in mind
to add some additional bytes here, too.
Thomas
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