Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755126AbaK0JMl (ORCPT ); Thu, 27 Nov 2014 04:12:41 -0500 Received: from cantor2.suse.de ([195.135.220.15]:60040 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754778AbaK0JMe (ORCPT ); Thu, 27 Nov 2014 04:12:34 -0500 Date: Thu, 27 Nov 2014 10:12:28 +0100 From: Borislav Petkov To: Boris Ostrovsky Cc: konrad.wilk@oracle.com, x86@kernel.org, gregkh@linuxfoundation.org, david.vrabel@citrix.com, stable@vger.kernel.org, rshendershot@mchsi.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode_ldr on 32-bit Message-ID: <20141127091228.GA4828@pd.tnic> References: 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 Wed, Nov 26, 2014 at 07:13:02PM -0800, Boris Ostrovsky wrote: > I was confusing you: accessing dis_ucode_ldr by virtual address does > work on PV. But we then fail later, in load_ucode_intel_ap(), because > it also tries to use __pa_nodebug() which can't be used by PV. > > So if accessing dis_ucode_ldr by virtual address is acceptable > (although I don't think it is?) then we can stick dis_ucode_ldr=1 into > xen_start_kernel() and then things look OK. > > A better solution may be to replace cpuid in x86_guest() with 'return > pv_info.paravirt_enabled' (or paravirt_enabled(), I guess). I gave > it a quick spin (32-bit only) and it seems to work. I'll see how my > overnight tests behave. Ok, but let's have a clean design: maybe have a weak default stub which returns false when PARAVIRT is not enabled in the .config and then add an override in, say, arch/x86/kernel/paravirt.c which returns true when running as a guest. Something like that, at least. I can imagine other stuff wanting to use the dynamic checking at runtime too... -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/