Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932762AbaLAWLg (ORCPT ); Mon, 1 Dec 2014 17:11:36 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:28215 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754026AbaLAWIf (ORCPT ); Mon, 1 Dec 2014 17:08:35 -0500 Date: Mon, 1 Dec 2014 16:57:25 -0500 From: Konrad Rzeszutek Wilk To: Boris Ostrovsky , gleb@kernel.org, pbonzini@redhat.com, kvm@vger.kernel.org Cc: bp@suse.de, x86@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, david.vrabel@citrix.com Subject: Re: [PATCH] x86, microcode: Don't initialize microcode code on paravirt Message-ID: <20141201215725.GG24289@laptop.dumpdata.com> References: <1417469264-31470-1-git-send-email-boris.ostrovsky@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1417469264-31470-1-git-send-email-boris.ostrovsky@oracle.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 01, 2014 at 04:27:44PM -0500, Boris Ostrovsky wrote: > Paravirtual guests are not expected to load microcode into processors > and therefore it is not necessary to initialize microcode loading > logic. CC-ing the KVM folks since they use the paravirt interface too. > > In fact, under certain circumstances initializing this logic may cause > the guest to crash. Specifically, 32-bit kernels use __pa_nodebug() > macro which does not work in Xen (the code path that leads to this macro > happens during resume when we call mc_bp_resume()->load_ucode_ap() > ->check_loader_disabled_ap()) > > Signed-off-by: Boris Ostrovsky > --- > arch/x86/kernel/cpu/microcode/core.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c > index 2ce9051..ebd232d 100644 > --- a/arch/x86/kernel/cpu/microcode/core.c > +++ b/arch/x86/kernel/cpu/microcode/core.c > @@ -557,7 +557,7 @@ static int __init microcode_init(void) > struct cpuinfo_x86 *c = &cpu_data(0); > int error; > > - if (dis_ucode_ldr) > + if (paravirt_enabled() || dis_ucode_ldr) > return 0; > > if (c->x86_vendor == X86_VENDOR_INTEL) > -- > 1.7.1 > -- 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/