linux-kernel - Re: Kernel broken on processors without performance counters

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Message-ID: <5808.1437505205@turing-police.cc.vt.edu>
Date:	Tue, 21 Jul 2015 15:00:05 -0400
From:	Valdis.Kletnieks@...edu
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jason Baron <jasonbaron0@...il.com>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Vince Weaver <vince@...ter.net>,
	"hillf.zj" <hillf.zj@...baba-inc.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Kernel broken on processors without performance counters

On Tue, 21 Jul 2015 11:54:30 -0700, Andy Lutomirski said:

> Could this be done at link time, or perhaps when compressing the
> kernel image, instead of at boot time?

That's only safe to do if the kernel is built for one specific CPU - if it's
a generic kernel that boots on multiple hardware designs, it will be wrong
for some systems.

In other words - safe to do if you're building it for *your* hardware. Totally
unsafe for a distro.

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