From: Li RongQing <roy.qing...@gmail.com> Date: Thu, 25 Feb 2016 09:50:41 +0800
> On Thu, Feb 25, 2016 at 5:44 AM, Stephen Hemminger > <step...@networkplumber.org> wrote: >>> This is especially annoying for the virtualization case because the >>> KVM's tap driver will by default adopt the bridge's MTU on startup >>> making it impossible (without the workaround) to use a large MTU on the >>> guest VMs. >>> >>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1399064 >> >> This use case looks like KVM misusing bridge MTU. I.e it should set TAP >> MTU to what it wants then enslave it, not vice versa. > > 1. a use should be able to configure an empty bridge MTU to a higher > mtu than 1500 > > 2. if first configure the tap MTU a higher value, other port is lower > value, the pmtu > will be used, it maybe lower performance. > the configuration process is written into libvirt, located in > virnetdevtap.c, of cause it can > be improved to fix this issue. > https://www.redhat.com/archives/libvir-list/2008-December/msg00083.html You are saying that it is possible to achieve the behavior the user wants with the mechanisms provided, which means this patch isn't necessary. And if I added the patch it would be of limited value, since proper software would have to cope with the behavior of older kernels anyways. I'm not applying this, sorry.
