From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760135AbcLPJVP (ORCPT ); Fri, 16 Dec 2016 04:21:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:36655 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759620AbcLPJUq (ORCPT ); Fri, 16 Dec 2016 04:20:46 -0500 Subject: Re: Can't boot as Xen dom0 due to commit fe055896 To: Borislav Petkov References: <73a4d64b-b139-6579-a560-92311641d6c7@suse.com> <20161215164635.thm7ruio2ddnxszw@pd.tnic> <20161215171755.xpfuax7a6q3jofet@pd.tnic> <20161215173609.ornfok6lk5oro2pj@pd.tnic> <20161216090228.ri4alokiaagqtibt@pd.tnic> Cc: Boris Ostrovsky , Linux Kernel Mailing List , xen-devel From: Juergen Gross Message-ID: <29d252b8-67ff-bd61-f274-0ed75708cd55@suse.com> Date: Fri, 16 Dec 2016 10:20:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20161216090228.ri4alokiaagqtibt@pd.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/12/16 10:02, Borislav Petkov wrote: > On Fri, Dec 16, 2016 at 08:28:46AM +0100, Juergen Gross wrote: >> Not trying to load ucode in _any_ guest is an optimization only. > > Does the hunk below work too? Without testing, but I doubt it is working. As pv guests aren't coming through check_loader_disabled_bsp() at all I can't see why your patch would work for dom0. Additionally I don't think you want to call native_cpuid() if have_cpuid_p() returns false. So I think you want a generic "platform_allows_ucode_load()" function checking for support of cpuid and virtualization. This function should be called both in check_loader_disabled_bsp() and check_loader_disabled_ap() to bail out early. Juergen > > I don't want to do hypervisor-specific solutions. > > --- > 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(); > >