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From: Joe Lawrence <joe.lawrence@redhat.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] docs/livepatch: Add new compiler considerations doc
Date: Wed, 22 Jul 2020 13:03:03 -0400
Message-ID: <de3672ef-8779-245f-943d-3d5a4b875446@redhat.com> (raw)
In-Reply-To: <20200721230442.5v6ah7bpjx4puqva@treble>

On 7/21/20 7:04 PM, Josh Poimboeuf wrote:
> On Tue, Jul 21, 2020 at 12:14:06PM -0400, Joe Lawrence wrote:
>> Compiler optimizations can have serious implications on livepatching.
>> Create a document that outlines common optimization patterns and safe
>> ways to livepatch them.
>>
>> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
> 
> There's a lot of good info here, but I wonder if it should be
> reorganized a bit and instead called "how to create a livepatch module",
> because that's really the point of it all.
> 

That would be nice.  Would you consider a stand-alone 
compiler-optimizations doc an incremental step towards that end?  Note 
that the other files (callbacks, shadow-vars, system-state) in their 
current form might be as confusing to the newbie.

> I'm thinking a newcomer reading this might be lost.  It's not
> necessarily clear that there are currently two completely different
> approaches to creating a livepatch module, each with their own quirks
> and benefits/drawbacks.  There is one mention of a "source-based
> livepatch author" but no explanation of what that means.
> 

Yes, the initial draft was light on source-based patching since I only 
really tinker with it for samples/kselftests.  The doc was the result of 
an experienced livepatch developer and Sunday afternoon w/the compiler. 
I'm sure it reads as such. :)

> Maybe it could begin with an overview of the two approaches, and then
> delve more into the details of each approach, and then delve even more
> into the gory details about compiler optimizations.
> 

Up until now, the livepatch documentation has danced around the 
particular creation method and only described the API in abstract.  If a 
compiler considerations doc needs to have that complete context then I'd 
suggest we reorganize the entire lot as a prerequisite.

> Also the kpatch-build section can reference the patch author guide which
> we have on github.
> 

Good point.  I think there are a few kpatch-specific implications 
(sibling call changes maybe) to consider.

-- Joe


  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21 16:14 [PATCH 0/2] livepatch: Add compiler optimization disclaimer/docs Joe Lawrence
2020-07-21 16:14 ` [PATCH 1/2] docs/livepatch: Add new compiler considerations doc Joe Lawrence
2020-07-21 23:04   ` Josh Poimboeuf
2020-07-22 17:03     ` Joe Lawrence [this message]
2020-07-22 20:51       ` Josh Poimboeuf
2020-08-06 12:03         ` Petr Mladek
2020-08-10 19:46           ` refactoring livepatch documentation was " Joe Lawrence
2020-07-21 16:14 ` [PATCH 2/2] samples/livepatch: Add README.rst disclaimer Joe Lawrence
2020-08-06 12:07   ` Petr Mladek

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