From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754650AbaISIDh (ORCPT ); Fri, 19 Sep 2014 04:03:37 -0400 Received: from mail.skyhub.de ([78.46.96.112]:51446 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754250AbaISIDc (ORCPT ); Fri, 19 Sep 2014 04:03:32 -0400 Date: Fri, 19 Sep 2014 10:03:22 +0200 From: Borislav Petkov To: Andy Lutomirski Cc: "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , Chuck Ebbert , Henrique de Moraes Holschuh Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability Message-ID: <20140919080322.GB30491@nazgul.tnic> References: <20140918135202.GA26038@khazad-dum.debian.net> <541B2F33.8000002@amacapital.net> <20140918145328.0253f009@as> <9c84cde6-3d70-4337-8738-0283d06d8cf0@email.android.com> <20140918200659.GA5331@khazad-dum.debian.net> <20140919001311.GB5331@khazad-dum.debian.net> <713c7342-bdf4-4e38-8de2-37d840d7028b@email.android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 18, 2014 at 06:00:12PM -0700, Andy Lutomirski wrote: > Yes, but how? I assume that BIOS isn't switching between two > different ucode blobs, and I don't know about any wrcpuid instruction. > So there must be *some* way, at least on new ucode (and maybe on old > ucode) to change that bit. I'd venture a guess that WRMSR to some reg should give you that, if they expose it. -- Regards/Gruss, Boris. --