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

On 28/03/2024 23:01, Peter Xu wrote: > On Thu, Mar 28, 2024 at 11:18:04AM -0300, Fabiano Rosas wrote: >> Philippe Mathieu-Daudé <philmd(a)linaro.org&gt; writes: >> >>> The whole RDMA subsystem was deprecated in commit e9a54265f5 >>> ("hw/rdma: Deprecate the pvrdma device and the rdma subsystem") >>> released in v8.2. >>> >>> Remove: >>> - RDMA handling from migration >>> - dependencies on libibumad, libibverbs and librdmacm >>> >>> Keep the RAM_SAVE_FLAG_HOOK definition since it might appears >>> in old migration streams. >>> >>> Cc: Peter Xu <peterx(a)redhat.com&gt; >>> Cc: Li Zhijian <lizhijian(a)fujitsu.com&gt; >>> Acked-by: Fabiano Rosas <farosas(a)suse.de&gt; >>> Signed-off-by: Philippe Mathieu-Daudé <philmd(a)linaro.org&gt; >> >> Just to be clear, because people raised the point in the last version, >> the first link in the deprecation commit links to a thread comprising >> entirely of rdma migration patches. I don't see any ambiguity on whether >> the deprecation was intended to include migration. There's even an ack >> from Juan. > > Yes I remember that's the plan. > >> >> So on the basis of not reverting the previous maintainer's decision, my >> Ack stands here. >> >> We also had pretty obvious bugs ([1], [2]) in the past that would have >> been caught if we had any kind of testing for the feature, so I can't >> even say this thing works currently. >> >> @Peter Xu, @Li Zhijian, what are your thoughts on this? > > Generally I definitely agree with such a removal sooner or later, as that's > how deprecation works, and even after Juan's left I'm not aware of any > other new RDMA users. Personally, I'd slightly prefer postponing it one > more release which might help a bit of our downstream maintenance, however > I assume that's not a blocker either, as I think we can also manage it. > > IMHO it's more important to know whether there are still users and whether > they would still like to see it around. That's also one thing I notice that > e9a54265f533f didn't yet get acks from RDMA users that we are aware, even > if they're rare. According to [2] it could be that such user may only rely > on the release versions of QEMU when it broke things. > > So I'm copying Yu too (while Zhijian is already in the loop), just in case > someone would like to stand up and speak. I admit RDMA migration was lack of testing(unit/CI test), which led to the a few obvious bugs being noticed too late. However I was a bit surprised when I saw the removal of the RDMA migration. I wasn't aware that this feature has not been marked as deprecated(at least there is no prompt to end-user). > IMHO it's more important to know whether there are still users and whether > they would still like to see it around. Agree. I didn't immediately express my opinion in V1 because I'm also consulting our customers for this feature in the future. Personally, I agree with Perter's idea that "I'd slightly prefer postponing it one more release which might help a bit of our downstream maintenance"

Thanks Zhijian > > Thanks, > >> >> 1- https://lore.kernel.org/r/20230920090412.726725-1-lizhijian@fujitsu.com >> 2- https://lore.kernel.org/r/CAHEcVy7HXSwn4Ow_Kog+Q+TN6f_kMeiCHevz1qGM-fbxBP... >>