linux-kernel - Re: [PATCH 0/4] objtool,perf: Use shared x86 insn decoder

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Message-ID: <20190831201931.GA18202@kernel.org>
Date:   Sat, 31 Aug 2019 17:19:31 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 0/4] objtool,perf: Use shared x86 insn decoder

Em Sat, Aug 31, 2019 at 10:51:52AM +0900, Masami Hiramatsu escreveu:
> On Fri, 30 Aug 2019 16:48:45 -0300
> Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> 
> > Em Fri, Aug 30, 2019 at 02:31:09PM -0500, Josh Poimboeuf escreveu:
> > > On Fri, Aug 30, 2019 at 04:00:58PM -0300, Arnaldo Carvalho de Melo wrote:
> > > > I.e. we need to make sure that it always gets the x86 stuff, not
> > > > something that is tied to the host arch, with the patch below we get it
> > > > to work, please take a look.
> > > > 
> > > > Probably this should go to the master copy, i.e. to the kernel sources,
> > > > no?
> 
> Interesting approach. Hmm, but I would like "diff -I" trick just
> for short term solution.

Ok, I'm in a hurry right now, plumbers and all, so I'll just add the
diff -I trick and will have your "I would like that trick" sentence
above as an Acked-by: you, ok?

- Arnaldo
 
> > > > That or we'll have to ask the check-headers.sh and objtool sync-check
> > > > (hey, this should be unified, each project could provide just the list
> > > > of things it uses, but I digress) to ignore those lines...
> > > > 
> > > > I.e. we want to decode intel_PT traces on other arches, ditto for
> > > > CoreSight (not affected here, but similar concept).
> > > > 
> > > > will kick the full container build process now.
> > > 
> > > Interesting, I didn't realize other arches would be using it.  The patch
> > 
> > Yeah, decoding CoreSight (aarch64) hardware traces on x86_64 should be
> > as possible as decoding Intel PT hardware traces on aarch64 :-)
> > 
> > > looks good to me.
> > > 
> > > Ideally there wouldn't be any differences between the headers, but if
> > > that's unavoidable then I guess we can just use the same 'diff -I' trick
> > 
> > I'll go with this now, but...
> > 
> > > we were using before in the check script(s).
> > 
> > Masami? What do you think of applying the patch to the main kernel
> > sources so that building a decoder for x86 on any other arch becomes
> > possible?
> 
> I think the build of kernel and user-space tools are different especially
> for "include/asm", since user-space tools may want to use all architecture
> features, but kernel needs only the architecture which it runs on.
> Maybe we need a special Makefile entries for the modules which depends
> on architecture dependent parts. e.g.
> 
> x86-objs = insn.o inat.o ...
> arm64-objs = coresight.o ...
> 
> and they should have different -I options ('-I arch/x86/include' or 
> '-I arch/arm64/include') for compiling.
> I think this is better and scalable, if you use common (clone) files in
> the kernel tree.
> 
> Thank you,
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>

-- 

- Arnaldo