linux-kernel - Re: [PATCH v10 1/8] crash: introduce arch/*/asm/crash.h

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Date:   Sat, 13 Aug 2022 08:24:35 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Eric DeVolder <eric.devolder@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, vgoyal@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
        sourabhjain@...ux.ibm.com, konrad.wilk@...cle.com,
        boris.ostrovsky@...cle.com
Subject: Re: [PATCH v10 1/8] crash: introduce arch/*/asm/crash.h

On 08/12/22 at 04:23pm, Eric DeVolder wrote:
> 
> 
> On 8/12/22 04:46, Baoquan He wrote:
> > On 08/08/22 at 10:18am, Eric DeVolder wrote:
> > > 
> > > 
> > > On 8/7/22 22:25, Baoquan He wrote:
> > > > Hi Eric,
> > > > 
> > > > On 07/21/22 at 02:17pm, Eric DeVolder wrote:
> > > > > The use of __weak is being eliminated within kexec sources.
> > > > > The technique uses macros mapped onto inline functions in
> > > > > order to replace __weak.
> > > > > 
> > > > > This patchset was using __weak and so in order to replace
> > > > > __weak, this patch introduces arch/*/asm/crash.h, patterned
> > > > > after how kexec is moving away from __weak and to the macro
> > > > > definitions.
> > > > 
> > > > Are you going to replace __weak in kexec of arll ARCHes? I don't see
> > > > your point why all these empty header files are introduced. Wondering
> > > > what's impacted if not adding these empty files?
> > > 
> > > Hi Baoquan,
> > > In this patchset, to file include/linux/crash_core.h I added the line #include <asm/crash.h>.
> > > I patterned this after how include/linux/kexec.h does #include <asm/kexec.h>.
> > 
> > I am sorry, Eric, it looks not so good. I understand you want to pattern
> > asm/kexe.h, but we need consider reality. Introducing a dozen of empty
> > header file and not being able to tell when they will be filled doesn't
> > make sense.
> > 
> > Includig <asm/crash.h> where needed is much simpler. I doubt if your way
> > can pass other reviewers' line. Can you reconsider?
> 
> If I include <asm/crash.h> where needed, which is kernel/crash_core.c, then
> the other archs will fail build if that file doesn't exist. A couple of
> options, which do you think is better to pursue?
> 
> - use asm/kexec.h instead of asm/crash.h; it appears all the architectures
> already have this file in place
> 
> - go ahead and put the appropriate crash macros/inline functions into each
> arch asm/crash.h so that the files are not just empty, and leave the use of
> asm/crash.h

I think we can do this in two steps.

Firstly, make do with asm/kexec.h since all other ARCHes put crash related stuff
into asm/kexec.h, except of x86. 

Secondly, clean up to put those crash marco/inline functions into
asm/crash.h.

The 2nd step can be done in a independent patchset. What do you think?