Re: [PATCH slof] virtio: Fix vring allocation

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

Alexey Kardashevskiy <aik@ozlabs.ru> writes:

> 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 <aik@ozlabs.ru>
> ---
>  lib/libvirtio/virtio.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c
> index b010796..22615c4 100644
> --- a/lib/libvirtio/virtio.c
> +++ b/lib/libvirtio/virtio.c
> @@ -33,7 +33,8 @@
>  unsigned long virtio_vring_size(unsigned int qsize)
>  {
>  	return VQ_ALIGN(sizeof(struct vring_desc) * qsize + 2 * (2 + qsize))

While at it, lets not have the above magic numbers as well ^^^^^^^^^^

sizeof(struct vring_avail) + sizeof(uint16_t) * qsize

> -		+ VQ_ALIGN(sizeof(struct vring_used_elem) * qsize);
> +               + VQ_ALIGN(sizeof(struct vring_used) +
> +                          sizeof(struct vring_used_elem) * qsize);
>  }
>
>
> -- 
> 2.0.0

Regards
Nikunj