Re: [virtio-dev] [PATCH] net: clarify device rules for mergeable buffers

On Tue, Mar 28, 2017 at 02:09:11AM +0300, Michael S. Tsirkin wrote:
> The idea behind mergeable buffers was to simply use them in a way
> similar to a chain of descriptors.  Unfortunately the current text does
> not say so - apparently nothing says device can't spread a packet over
> as many buffers as it likes - but this didn't prevent drivers from
> relying on buffers being used as a chain of descriptors, completely -
> and blindly accessing it without checking the length at least for the
> packet header.
> 
> Let's just make the spec match this reality - if devices ever want more
> flexibility, we can add a feature bit.
> 
> Further, correct all misuses of a "descriptor" to "buffer" as that
> is the entity that is being merged.
> 
> VIRTIO-160
> 
> Signed-off-by: Michael S. Tsirkin <>
> ---
>  content.tex | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)

Reviewed-by: Stefan Hajnoczi <>