linux-kernel - Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 12 Jun 2012 13:58:23 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, andi@...stfloor.org, mingo@...e.hu,
	ming.m.lin@...el.com, "Yu, Fenghua" <fenghua.yu@...el.com>
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

On 06/12/2012 01:56 PM, Borislav Petkov wrote:
> On Tue, Jun 12, 2012 at 01:42:07PM -0700, H. Peter Anvin wrote:
>> I personally don't know of any valid use case for per-core loads, and
>> it sounds like a horrid idea.
> 
> Vehemently agreed.
> 
> However, last time we talked about Ingo mentioned some possibility
> of having different microcode versions on different CPUs:
> http://lkml.indiana.edu/hypermail/linux/kernel/1105.3/00749.html
> 
> Hmm...
> 
>> And yes, I would prefer a single sysfs file, or better yet a plain old
>> device node.
> 
> Also agreed.
> 

There is a difference here.  Mixed steppings or even mixed CPUs are,
indeed, supported (even things like Nehalem + Westmere in the same
system).  However, the notion is that we should upload the *entire set*
of microcodes to the kernel, and let it flash the appropriate one into
each CPU.

This may result in different version number on different CPUs.

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/