From: Borislav Petkov <bp@alien8.de>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
"H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability
Date: Thu, 25 Sep 2014 10:51:58 +0200 [thread overview]
Message-ID: <20140925085158.GF22317@nazgul.tnic> (raw)
In-Reply-To: <20140924145658.GB31678@khazad-dum.debian.net>
On Wed, Sep 24, 2014 at 11:56:58AM -0300, Henrique de Moraes Holschuh wrote:
> I don't know about AMD, but on Intel, the time it takes to update the
> microcode on a core is anything but negligible[1], so the microcode
> version skew window still exists, and it is not small. It is much smaller
> than it once was, but it is still there.
I think that window is unsafe but yeah, we probably should take your
empirical observation as good enough for now.
> But IMHO we still need to detect and do something smart when
> x86_capability changes due to a microcode update.
>
> And I'd really prefer it to be "update x86_capability, warn the user and
> carry on" for anything that is not going to crash the kernel.
The problem is with hiding CPUID bits and userspace using HLE after
having detected it previously. I think we'll be on the safe side if we
reboot thus the suggestion to the user that rebooting should be done
ASAP.
--
Regards/Gruss,
Boris.
--
next prev parent reply other threads:[~2014-09-25 8:52 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-18 13:52 x86, microcode: BUG: microcode update that changes x86_capability Henrique de Moraes Holschuh
2014-09-18 19:14 ` Andy Lutomirski
2014-09-18 19:53 ` Chuck Ebbert
2014-09-18 19:55 ` H. Peter Anvin
2014-09-18 20:06 ` Henrique de Moraes Holschuh
2014-09-19 0:13 ` Henrique de Moraes Holschuh
2014-09-19 0:23 ` Andy Lutomirski
2014-09-19 0:28 ` H. Peter Anvin
2014-09-19 1:00 ` Andy Lutomirski
2014-09-19 8:03 ` Borislav Petkov
2014-09-19 11:00 ` Henrique de Moraes Holschuh
2014-09-19 11:29 ` Borislav Petkov
2014-09-19 12:54 ` Chuck Ebbert
2014-09-19 13:14 ` Josh Boyer
2014-09-19 13:37 ` Chuck Ebbert
2014-09-19 15:00 ` Borislav Petkov
2014-09-19 16:13 ` Andy Lutomirski
2014-09-19 16:54 ` Henrique de Moraes Holschuh
2014-09-19 16:42 ` Henrique de Moraes Holschuh
2014-09-23 20:00 ` Borislav Petkov
2014-09-24 14:56 ` Henrique de Moraes Holschuh
2014-09-24 15:00 ` Andy Lutomirski
2014-09-24 17:45 ` Henrique de Moraes Holschuh
2014-09-24 17:48 ` Andy Lutomirski
2014-09-24 18:59 ` Henrique de Moraes Holschuh
2014-09-24 19:34 ` Andy Lutomirski
2014-09-25 8:57 ` Borislav Petkov
2014-09-25 8:51 ` Borislav Petkov [this message]
2014-09-25 11:36 ` Henrique de Moraes Holschuh
2014-09-25 12:10 ` Borislav Petkov
2014-09-25 14:40 ` Henrique de Moraes Holschuh
2014-09-25 14:56 ` Borislav Petkov
2014-09-25 15:30 ` Henrique de Moraes Holschuh
2014-09-25 15:50 ` Borislav Petkov
2014-09-25 16:41 ` Henrique de Moraes Holschuh
2014-09-25 16:57 ` Borislav Petkov
2014-09-25 17:09 ` Henrique de Moraes Holschuh
2014-09-19 13:51 ` Henrique de Moraes Holschuh
2014-09-19 14:49 ` Borislav Petkov
2014-09-19 17:22 ` Henrique de Moraes Holschuh
2014-09-19 22:35 ` Henrique de Moraes Holschuh
2014-09-29 11:51 ` Henrique de Moraes Holschuh
2014-09-19 9:56 ` Henrique de Moraes Holschuh
2014-09-19 16:11 ` Henrique de Moraes Holschuh
2014-09-22 0:37 ` Andi Kleen
2014-09-22 0:51 ` H. Peter Anvin
2014-09-22 0:58 ` Andi Kleen
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