Hyperv: netvsc: Set net_dev's recv buffer size according to NVSP protocol version

[honzhan_microsoft.com]

Summary

If the NVSP protocol version is not greater than NVSP_PROTOCOL_VERSION_2, then
the recv buffer size is 15MB, otherwise the buffer size is 16MB.

Submitted by: Hongjiang Zhang <honzhan microsoft com>

[decui_microsoft.com]

looks good to me.

[royger]

I don't mind committing this, but is it really worth it? I mean, with 16MB you are always on the safe side, and it's not like 1MB of memory is a huge deal this days...

[decui_microsoft.com]

In D4814#103342, @royger wrote:

I don't mind committing this, but is it really worth it? I mean, with 16MB you are always on the safe side, and it's not like 1MB of memory is a huge deal this days...

It's only to cope with a host bug of Hyper-V 2008R2 -- on this old host, we need to use a slightly smaller receive buffer size, otherwise the buffer will not be accepted by the host.