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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 363D4140004 X-Rspamd-Server: rspam07 X-Stat-Signature: 5t697haa7rs5czzpznurgwn433yrku3t X-Rspam-User: X-HE-Tag: 1763059119-797825 X-HE-Meta: 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 2r0bw0Q2 1s7+n+CowLYWibEXz8UGgunXJvjQ1E8HdEWQvk2d1zjZ4Wb9j7x4Vk9n/6W+GhQuRNTSZH6O9xXagE12K6CFJYoxEKaUkE3LOXMtnr8PxG/tD+UzUfiPgIQnaRb2in7YHE5BADf8CNFwr1YGtcXXfPR2YUh4+O42RpfHBUlxZylQusa7mT2fibXM6u9gcVp+RqohwhtToYjNTrzjvaOMvUWAM76VN1Ztjiys6y2VhhnSO2zX7F5qnLlT2dy1BAMWhlCfyuUhu6Mqwv+Fqbz+YkuQPxCC0bKfF0SN7kJSqy/SwBWaVae5TDxDmASapKW+E4Z7Vj/Bu9X8iwhQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Nov 13, 2025 at 11:32=E2=80=AFAM Mike Rapoport wr= ote: > > On Wed, Nov 12, 2025 at 09:58:27AM -0500, Pasha Tatashin wrote: > > On Wed, Nov 12, 2025 at 8:25=E2=80=AFAM Mike Rapoport = wrote: > > > > > > Hi Pasha, > > > > > > On Tue, Nov 11, 2025 at 03:57:39PM -0500, Pasha Tatashin wrote: > > > > Hi Mike, > > > > > > > > Thank you for review, my comments below: > > > > > > > > > > This is why this call is placed first in reboot(), before any > > > > > > irreversible reboot notifiers or shutdown callbacks are perform= ed. If > > > > > > an allocation problem occurs in KHO, the error is simply report= ed back > > > > > > to userspace, and the live update update is safely aborted. > > > > > > The call to liveupdate_reboot() is just before kernel_kexec(). Why we= don't > > > move it there? > > > > Yes, I can move that call into kernel_kexec(). > > > > > And all the liveupdate_reboot() does if kho_finalize() fails it's mas= saging > > > the error value before returning it to userspace. Why kernel_kexec() = can't > > > do the same? > > > > We could do that. It would look something like this: > > > > if (liveupdate_enabled()) > > kho_finalize(); > > > > Because we want to do kho_finalize() from kernel_kexec only when we do > > live update. > > > > > > > This is fine. But what I don't like is that we can't use kho with= out > > > > > liveupdate. We are making debugfs optional, we have a way to call > > > > This is exactly the fix I proposed: > > > > 1. When live-update is enabled, always disable "finalize" debugfs API. > > 2. When live-update is disabled, always enable "finalize" debugfs API. > > I don't mind the concept, what I do mind is sprinkling liveupdate_enabled= () > in KHO. Sure, let's just unconditionally do kho_fill_kimage(). > How about we kill debugfs/kho/out/abort and make kho_finalize() overwrite > an existing FDT if there was any? > > Abort was required to allow rollback for subsystems that had kho notifier= s, > but now notifiers are gone and kho_abort() only frees the memory > serialization data. I don't see an issue with kho_finalize() from debugfs > being a tad slower because of a call to kho_abort() and the liveupdate pa= th > anyway won't incur that penalty. Sounds good to me. > > > KHO should not call into liveupdate. That's layering violation. > > > And "stateless KHO" does not really make it stateless, it only remove= s the > > > memory serialization from kho_finalize(), but it's still required to = pack > > > the FDT. > > > > This touches on a point I've raised in the KHO sync meetings: to be > > effective, the "stateless KHO" work must also make subtree add/remove > > stateless. There should not be a separate "finalize" state just to > > finish the FDT. The KHO FDT is tiny (only one page), and there are > > only a handful of subtrees. Adding and removing subtrees is cheap; we > > should be able to open FDT, modify it, and finish FDT on every > > operation. There's no need for a special finalization state at kexec > > time. KHO should be totally stateless. > > And as the first step we can drop 'if (!kho_out.finalized)' from > kho_fill_kimage(). We might need to massage the check for valid FDT in > kho_populate() to avoid unnecessary noise, but largely there's no issue > with always passing KHO data in kimage. Sounds good, let me work on this patch. Pasha