linux-kernel - Re: [PATCH 3/6] x86/mce: Add support for new MCA

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Message-ID: <20160708094653.GC13849@gmail.com>
Date:	Fri, 8 Jul 2016 11:46:53 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Yazen Ghannam <Yazen.Ghannam@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 3/6] x86/mce: Add support for new MCA_SYND register

* Borislav Petkov <bp@...en8.de> wrote:

> On Fri, Jul 08, 2016 at 11:26:59AM +0200, Ingo Molnar wrote:
> > So why does neither the changelog nor the code comment actually _explain_ this and 
> > give aa bit of a background about what 'syndrome information' is and why we want 
> > to have kernel support for it?
> > 
> > This is why I hate kernel tooling that is not part of the kernel tree - the mcelog 
> > patch (hopefully ...) would tell us more about all this - but it's separate and 
> > this patch does not tell us anything ...
> 
> Ah, this is one of those omissions where we forgot to explain, sorry.
> How about this:
> 
> "The syndrome value is used to uniquely identify which bits of a
> reported ECC error are corrupted."

I'm not sure I can parse that: how can a reported error have bits corrupted?

Or is this about various details about the location of the error (normally 
contained in a 'struct mce' entry), and the 'syndrome value' further qualifies 
that information by telling us which fields of those records are reliable?

I.e. a bit more context would be nice. You cannot go wrong if you assume that 
readers of changelogs (and maintainers in particular) have the attention span
of a slightly retarded golden retriever.

> Do you want it as a comment in the code or in the commit message or both?

I'm fine with an add-on patch that adds a good explanation for all this to the 
code.

Thanks,

	Ingo