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envelope-from=manish.mishra@nutanix.com; helo=mx0b-002c1b01.pphosted.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 21/10/22 3:37 am, Daniel P. Berrangé wrote: > On Thu, Oct 20, 2022 at 12:32:06PM -0400, Peter Xu wrote: >> On Thu, Oct 20, 2022 at 08:14:19PM +0530, manish.mishra wrote: >>> I had one concern, during recover we do not send any magic. As of now we >> do not support multifd with postcopy so it should be fine, we can do >> explict checking for non-recovery case. But i remember from some >> discussion in future there may be support for multiFD with postcopy or >> have multiple postcopy preempt channels too, then proper handshake will >> be required? So at some point we want to take that path? For now i agree >> approach 1 will be good as suggested by Daniel it can be backported >> easily to older qemu's too. >> >> Yes for the long run I think we should provide a generic solution for all >> the channels to be established for migration purpose. >> >> Not to mention that as I replied previously to my original email, the trick >> won't easily work with dest QEMU where we need further change to allow qemu >> to accept new channels during loading of the VM. >> >> Considering the complexity that it'll take just to resolve the prempt >> channel ordering, I think maybe it's cleaner we just look for the long term >> goal. > I think we should just ignore the preempt channel. Lets just do the > easy bit and fix the main vs multifd channel mixup, as that's the one > that is definitely actively hitting people today. We can solve that as > a quick win in a way that is easy to backport to existing releases of > QEMU for those affected. Yes, that works for now Daniel. I can send a patch as per your earlier suggestions on this, early next week if it fine? > Separately from that, lets define a clean slate migration protocol to > solve many of our historic problems and mistakes that can't be dealt > with through retrofitting, not limited to just this ordering mistake. > > We had a significant discussion about it at the start of the year > in this thread, which I think we should take forward and write into > a formal protocol spec. > > https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.gnu.org_archive_html_qemu-2Ddevel_2022-2D03_msg03655.html&d=DwIBaQ&c=s883GpUCOChKOHiocYtGcg&r=c4KON2DiMd-szjwjggQcuUvTsPWblztAL0gVzaHnNmc&m=vjRKUpojJeAWFcJNi7YETWaLjjOcLWIcdk8KO-HMu8_A3veG2aaGmZoLxFVHgLt0&s=uv5cKdIMcT8Wo3erYQZJqnMXvRCbda4gNtxsy9EXrC8&e= This was a good read for me. :) > > With regards, > Daniel Thanks Manish Mishra