From: Jiri Kosina <jkosina@suse.cz>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Slaby <jslaby@suse.cz>,
live-patching@vger.kernel.org, sjenning@redhat.com,
vojtech@suse.cz, mingo@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC kgr on klp 0/9] kGraft on the top of KLP
Date: Tue, 5 May 2015 00:48:22 +0200 (CEST) [thread overview]
Message-ID: <alpine.LNX.2.00.1505050036440.17961@pobox.suse.cz> (raw)
In-Reply-To: <20150504154429.GA21537@treble.redhat.com>
On Mon, 4 May 2015, Josh Poimboeuf wrote:
> Why do we need multiple consistency models?
Well, I am pretty sure we need always at least two:
- the "immediate" one, where the code redirection flip is switched
unconditionally and immediately (i.e. exactly what we currently have in
Linus' tree); semantically applicable to many patches, but not all of
them
- something that fills the "but not all of them" gap above.
Both of the solutions that have been presnted so far have some drawbacks
that need to be discussed further. To me, the "highlights" (in the
"drawbacks" space) are:
- any method that is stack-checking-based basically means that we have to
functionally 100% rely on stack unwinding correctness. We have never
done that before, and current stack unwinder is not ready for that
(Josh is working on improving that); plus it can cause the patching to
fail under certain circumstances
- the kGraft method is not (yet) able to patch kernel threads, and allows
for multiple instances of the patched functions to be running in
parallel (i.e. patch author needs to be aware of this constaint, and
write the code accordingly)
This is exactly why we are submitting the kGraft-on-klp patchset, so that
we have concurrent implementations (sharing the same goal) to compare, and
ultimately merge whatever the best possible outcome will be.
Thanks,
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2015-05-04 22:48 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-04 11:40 [RFC kgr on klp 1/9] livepatch: make kobject in klp_object statically allocated Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 2/9] livepatch: introduce patch/func-walking helpers Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 3/9] livepatch: add klp_*_to_patch helpers Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 4/9] livepatch: add kgr infrastructure Jiri Slaby
2015-05-04 12:23 ` Martin Schwidefsky
2015-05-05 13:27 ` Jiri Slaby
2015-05-05 14:34 ` Martin Schwidefsky
2015-05-04 11:40 ` [RFC kgr on klp 5/9] livepatch: teach klp about consistency models Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 6/9] livepatch: do not allow failure while really patching Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 7/9] livepatch: propagate the patch status to functions Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 8/9] livepatch: add kgraft-like patching Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 9/9] livepatch: send a fake signal to all tasks Jiri Slaby
2015-05-04 14:34 ` Oleg Nesterov
2015-05-06 12:58 ` Miroslav Benes
2015-05-04 12:20 ` [RFC kgr on klp 0/9] kGraft on the top of KLP Jiri Slaby
2015-05-04 15:44 ` Josh Poimboeuf
2015-05-04 22:48 ` Jiri Kosina [this message]
2015-05-05 3:43 ` Josh Poimboeuf
2015-05-05 6:14 ` Jiri Kosina
2015-05-05 16:24 ` Josh Poimboeuf
2015-05-12 9:45 ` Jiri Kosina
2015-05-12 15:20 ` Josh Poimboeuf
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