From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765848AbZAPXWa (ORCPT ); Fri, 16 Jan 2009 18:22:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751338AbZAPXWT (ORCPT ); Fri, 16 Jan 2009 18:22:19 -0500 Received: from relay2.sgi.com ([192.48.179.30]:35793 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1761563AbZAPXWS (ORCPT ); Fri, 16 Jan 2009 18:22:18 -0500 Message-ID: <497116A8.5080900@sgi.com> Date: Fri, 16 Jan 2009 15:22:16 -0800 From: Mike Travis User-Agent: Thunderbird 2.0.0.6 (X11/20070801) MIME-Version: 1.0 To: Ingo Molnar CC: LKML Subject: [PATCH] x86: put trigger in to detect mismatched apic versions. References: <49704DF6.8040205@sgi.com> <20090116092540.GC4305@elte.hu> <4970C984.30202@sgi.com> <20090116223011.GB3899@elte.hu> In-Reply-To: <20090116223011.GB3899@elte.hu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * Mike Travis wrote: > >> Hi Ingo, >> >> I did notice that the versions all came up the same, and that the checks >> were very specific. I was trying to be as transparent and unintrusive >> as possible. Since there's so few calls, I though this was a good >> approach but apparently I was wrong. >> >> I like the idea of collapsing the array down to one and checking to see >> if all apic's have the same version, but is this really the case? Must >> all apics be the same? > > Could you please send a patch that doesnt change the code, only adds a > 'boot APIC version' kind of variable as an apic_version __read_mostly > variable and does a WARN_ONCE() if that mismatches? We can then stick that > into -tip and see whether it triggers. > > The max array size is ~128K, right? So if the WARN_ONCE() does not > trigger, we can just drop the array and use the central apic_version > variable ... > > And even if it _does_ trigger, the version incompatibilities between APIC > protocols are very rare. They only happen across wildly different CPU > architectures like when going from very old external apics to integrated > apics, or going from apics to x-apics. We wont see any mixing across those > boundaries. > > Ingo Btw, I checked with our UV architect and the problem is that we need a 16 bit apic id which is what caused the MAX_APICS to be bumped to 32k. The lower 8 bits are the normal apic id, and the upper bit relate to the node. This means cpu 0 on node 0 has the same apic id as cpu 0 on node 1, etc. I also asked about whether we could rely on always having the same apic version, and the answer was yes, though it's really only relevant between the cpus on a node. Thanks, Mike --- Subject: x86: put trigger in to detect mismatched apic versions. Fire off one message if two apic's discovered with different apic versions. Signed-off-by: Mike Travis --- arch/x86/kernel/apic.c | 5 +++++ 1 file changed, 5 insertions(+) --- linux-2.6-for-ingo.orig/arch/x86/kernel/apic.c +++ linux-2.6-for-ingo/arch/x86/kernel/apic.c @@ -1833,6 +1833,11 @@ void __cpuinit generic_processor_info(in num_processors++; cpu = cpumask_next_zero(-1, cpu_present_mask); + if (version != apic_version[boot_cpu_physical_apicid]) + WARN_ONCE(1, + "ACPI: apic version mismatch, bootcpu: %x cpu %d: %x\n", + apic_version[boot_cpu_physical_apicid], cpu, version); + physid_set(apicid, phys_cpu_present_map); if (apicid == boot_cpu_physical_apicid) { /*