Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling

We use a batch of regression test cases for the stack, which covers the test for QEMU. I did such test for most of the QEMU releases planned as candidates for rollout. The migration test needs a pair of (either physical or virtual) servers with InfiniBand network, which makes it difficult to do on a single server. The nested VM could be a possible approach, for which we may need virtual InfiniBand network. Is SoftRoCE [1] a choice? I will try it and let you know. [1] https://enterprise-support.nvidia.com/s/article/howto-configure-soft-roce Thanks and best regards! On Thu, Apr 11, 2024 at 4:20 PM Peter Xu <peterx(a)redhat.com&gt; wrote: > > On Wed, Apr 10, 2024 at 09:49:15AM -0400, Peter Xu wrote: > > On Wed, Apr 10, 2024 at 02:28:59AM +0000, Zhijian Li (Fujitsu) via wrote: > > > > > > > > > on 4/10/2024 3:46 AM, Peter Xu wrote: > > > > > > >> Is there document/link about the unittest/CI for migration tests, Why > > > >> are those tests missing? > > > >> Is it hard or very special to set up an environment for that? maybe we > > > >> can help in this regards. > > > > See tests/qtest/migration-test.c. We put most of our migration tests > > > > there and that's covered in CI. > > > > > > > > I think one major issue is CI systems don't normally have rdma devices. > > > > Can rdma migration test be carried out without a real hardware? > > > > > > Yeah, RXE aka. SOFT-RoCE is able to emulate the RDMA, for example > > > $ sudo rdma link add rxe_eth0 type rxe netdev eth0 # on host > > > then we can get a new RDMA interface "rxe_eth0". > > > This new RDMA interface is able to do the QEMU RDMA migration. > > > > > > Also, the loopback(lo) device is able to emulate the RDMA interface > > > "rxe_lo", however when > > > I tried(years ago) to do RDMA migration over this > > > interface(rdma:127.0.0.1:3333) , it got something wrong. > > > So i gave up enabling the RDMA migration qtest at that time. > > > > Thanks, Zhijian. > > > > I'm not sure adding an emu-link for rdma is doable for CI systems, though. > > Maybe someone more familiar with how CI works can chim in. > > Some people got dropped on the cc list for unknown reason, I'm adding them > back (Fabiano, Peter Maydell, Phil). Let's make sure nobody is dropped by > accident. > > I'll try to summarize what is still missing, and I think these will be > greatly helpful if we don't want to deprecate rdma migration: > > 1) Either a CI test covering at least the major RDMA paths, or at least > periodically tests for each QEMU release will be needed. > > 2) Some performance tests between modern RDMA and NIC devices are > welcomed. The current knowledge is modern NIC can work similarly to > RDMA in performance, then it's debatable why we still maintain so much > rdma specific code. > > 3) No need to be soild patchsets for this one, but some plan to improve > RDMA migration code so that it is not almost isolated from the rest > protocols. > > 4) Someone to look after this code for real. > > For 2) and 3) more info is here: > > https://lore.kernel.org/r/ZhWa0YeAb9ySVKD1@x1n > > Here 4) can be the most important as Markus pointed out. We just didn't > get there yet on the discussions, but maybe Markus is right that we should > talk that first. > > Thanks, > > -- > Peter Xu >