[Qemu-devel] Re: qemu: async sending in tap causes "NFS not responding" error

[Sven Rudolph]

Scott Tsai <address@hidden> writes:

> I recently found that this chageset:
> http://git.savannah.gnu.org/cgit/qemu.git/commit/?id=e19eb22486f258a421108ac22b8380a4e2f16b97
> "net: make use of async packet sending API in tap client"
> causes NFS root Linux guest setups using TAP networking to fail with
> error messages like:
> nfs: server 172.20.0.1 not responding, still trying
> nfs: server 172.20.0.1 OK
> < .... repeat infinitely ...>
> This happens on both the "master" and "stable-0.11" branches on qemu.
>
> The attached '0001-net-revert-e19eb22486f258a421108ac22b8380a4e2f16b97.patch'
> makes NFS root on qemu emulated "arm-integrator-cp" boards work for me
> again.

> After finding:
> http://lists.gnu.org/archive/html/qemu-devel/2009-09/msg01173.html
> through Google and reading through the potentially bad commits that
> Sven found through bisection,
> I patched "tap_send()" to not run in a loop ("drain the tap send queue
> in one go"?) and the error goes away.

Thank you for digging into this. I tested your patch in my environment
and can confirm that it solves the problem.

        Sven