Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757382AbaFTRru (ORCPT ); Fri, 20 Jun 2014 13:47:50 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47498 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752153AbaFTRrt (ORCPT ); Fri, 20 Jun 2014 13:47:49 -0400 Message-ID: <53A473AA.7050301@zytor.com> Date: Fri, 20 Jun 2014 10:47:22 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Borislav Petkov CC: Dave Hansen , linux-kernel@vger.kernel.org, x86@kernel.org, Andi Kleen Subject: Re: [RFC][PATCH 3/3] x86: make MP a required-feature on 64-bit References: <20140620161736.D6AC16FD@viggo.jf.intel.com> <20140620161740.BFB00798@viggo.jf.intel.com> <53A46008.5060509@zytor.com> <53A4619C.8020100@sr71.net> <53A46365.6090101@zytor.com> <20140620174345.GD11391@pd.tnic> In-Reply-To: <20140620174345.GD11391@pd.tnic> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2014 10:43 AM, Borislav Petkov wrote: > On Fri, Jun 20, 2014 at 09:37:57AM -0700, H. Peter Anvin wrote: >> We probably should just the cpu_has_mp macro entirely. All it is used >> for is printing a warning in amd_k7_smp_check(). >> >> Andi, Borislav -- as far as I can tell, we have *never* enforced this on >> the 64-bit kernel, although we have enforced it on 64-bit processors >> running the 32-bit kernel. We should either enforce it on both or just >> drop it. What is your opinion? > > Well, my AMD CPUID guide says CPUID Fn8000_0001_EDX[19] is reserved, > i.e. that X86_FEATURE_MP bit will be probably cleared. > > And so it is, on my F15h AMD it is not set: > > eax in: 0x80000001, eax = 00600f20 ebx = 10000000 ecx = 01ebbfff edx = 2fd3fbff > ^ > ----------| > > So I don't think we should enforce it on 64-bit. > > I guess we can leave the check in amd_k7_smp_check() though but remove that > nasty cpu_has_mp macro and do static_cpu_has() instead. > > My 2ยข only. > This is run before static_cpu_has(). The point, though, was that we "enforce" (taint) on 32 bits but not on 64 bits, which is clearly wrong. My inclination is to completely kill amd_k7_smp_check() entirely, since noone seems to know when it actually matters and it is clearly historic. -hpa -- 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/