linux-kernel - Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code

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Date:	Fri, 11 Mar 2016 10:13:01 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@....com>
Cc:	bp@...e.de, hpa@...or.com, tglx@...utronix.de, mcgrof@...e.com,
	jgross@...e.com, paul.gortmaker@...driver.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/mtrr: Refactor PAT initialization code

* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Toshi Kani <toshi.kani@....com> wrote:
> 
> > MTRR manages PAT initialization as it implements a rendezvous
> > handler that initializes PAT as part of MTRR initialization.
> > 
> > When CPU does not support MTRR, ex. qemu32 virtual CPU, MTRR
> > simply skips PAT init, which causes PAT left enabled without
> > initialization. [...]
> 
> What practical effects does this have to the user? Does the kernel crash?

Btw., I find this omission _highly_ annoying: describing what negative effects a 
bug _causes in practice_ is the most important part of a changelog. How on earth 
can an experienced contributor omit such an important component from a patch 
description?

Most readers of changelogs couldn't care less about technical details of how the 
bug is fixed (of course others will read it so it's nice to have too), but what 
symptoms a bug causes, how serious is it, whether it should be backported are like 
super important compared to everything else you wrote - and both the description 
and the changelogs are totally silent on those topics ...

I've seen this in other PAT patches - please try to improve this.

Thanks,

	Ingo