Re: [dpdk-dev] [PATCH] virtio: fix the vq size issue

["Xie, Huawei" <huawei.xie@intel.com>]

On 7/1/2015 3:49 PM, Ouyang Changchun wrote:
> This commit breaks virtio basic packets rx functionality:
>   d78deadae4dca240e85054bf2d604a801676becc
>
> The QEMU use 256 as default vring size, also use this default value to calculate the virtio
> avail ring base address and used ring base address, and vhost in the backend use the ring base
> address to do packet IO.
>
> Virtio spec also says the queue size in PCI configuration is read-only, so virtio front end
> can't change it. just need use the read-only value to allocate space for vring and calculate the
> avail and used ring base address. Otherwise, the avail and used ring base address will be different
> between host and guest, accordingly, packet IO can't work normally.
virtio driver could still use the vq_size to initialize avail ring and
use ring so that they still have the same base address.
The other issue is vhost use  index & (vq->size -1) to index the ring.


Thomas:
This fix works but introduces slight change with original code. Could we
just rollback that commit?

d78deadae4dca240e85054bf2d604a801676becc


>
> Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c | 14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
>
>