From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759655AbcLPJBS (ORCPT ); Fri, 16 Dec 2016 04:01:18 -0500 Received: from mx2.suse.de ([195.135.220.15]:33894 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759582AbcLPJBG (ORCPT ); Fri, 16 Dec 2016 04:01:06 -0500 Date: Fri, 16 Dec 2016 10:01:00 +0100 From: Borislav Petkov To: Boris Ostrovsky Cc: Juergen Gross , Linux Kernel Mailing List , xen-devel Subject: Re: Can't boot as Xen dom0 due to commit fe055896 Message-ID: <20161216090100.cekw347kly3qd7c6@pd.tnic> References: <20161215171755.xpfuax7a6q3jofet@pd.tnic> <20161215173609.ornfok6lk5oro2pj@pd.tnic> <385ac3cd-7a3f-4c4d-69bb-8feee235fb7e@oracle.com> <20161215192305.dlgyrmteirgzop4y@pd.tnic> <399c758a-a94b-8aa1-efbb-79a0161b8020@oracle.com> <20161215200324.6ju7o5e3aiirrycf@pd.tnic> <51f0a58d-a5bc-aae4-22b2-f45bf7164088@oracle.com> <20161215230433.m52cs2gef662c2s7@pd.tnic> <539c1b43-009d-9a59-0c80-7b1e552ab0ed@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <539c1b43-009d-9a59-0c80-7b1e552ab0ed@oracle.com> User-Agent: NeoMutt/20161014 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 15, 2016 at 10:56:25PM -0500, Boris Ostrovsky wrote: > You can use xen_cpuid_base(), for example. It will prevent microcode loading Actually I want to do this at the end. CPUID(1).ECX[31] is reserved by both vendors for hypervisor use. > True. But I don't think it's clear that the problem we are seeing is > Xen-specific. If you can trigger it on baremetal, I'm all ears. --- diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 6996413c78c3..54219f619205 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -76,6 +76,7 @@ struct cpu_info_ctx { static bool __init check_loader_disabled_bsp(void) { static const char *__dis_opt_str = "dis_ucode_ldr"; + u32 a, b, c, d; #ifdef CONFIG_X86_32 const char *cmdline = (const char *)__pa_nodebug(boot_command_line); @@ -91,6 +92,17 @@ static bool __init check_loader_disabled_bsp(void) if (cmdline_find_option_bool(cmdline, option)) *res = true; + if (!have_cpuid_p()) + *res = true; + + a = 1; + c = 0; + native_cpuid(&a, &b, &c, &d); + + /* CPUID(1).ECX[31]: reserved for hypervisor use */ + if (c & BIT(31)) + *res = true; + return *res; } @@ -121,9 +133,6 @@ void __init load_ucode_bsp(void) if (check_loader_disabled_bsp()) return; - if (!have_cpuid_p()) - return; - vendor = x86_cpuid_vendor(); family = x86_cpuid_family(); @@ -157,9 +166,6 @@ void load_ucode_ap(void) if (check_loader_disabled_ap()) return; - if (!have_cpuid_p()) - return; - vendor = x86_cpuid_vendor(); family = x86_cpuid_family(); -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --