Negotiate the virtio ring size. The host may allow for very large
rings but application may only want a smaller ring.
Conversely, if the number of descriptors requested exceeds the virtio
host queue size, then just silently use the smaller host size.
This fixes issues with virtio in non-QEMU envirionments.
For example Google Compute Engine allows up to 16K elements
in ring.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Changchun Ouyang <changchun.ouyang@intel.com>
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