From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754224AbcKLWGT (ORCPT ); Sat, 12 Nov 2016 17:06:19 -0500 Received: from aibo.runbox.com ([91.220.196.211]:49428 "EHLO aibo.runbox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752870AbcKLWGS (ORCPT ); Sat, 12 Nov 2016 17:06:18 -0500 From: "M. Vefa Bicakci" Subject: Re: [PATCH] x86/cpuid: Deal with broken firmware once more To: Boris Ostrovsky References: <20161102122557.qs4rl6mb7n7l7j7p@linutronix.de> <24e69019-60d0-29e7-e31f-c6f00f9ed98a@brocade.com> <58e229e2-91f4-a97f-1b9f-089f48ef994a@brocade.com> <86609338-2b45-ed7e-fb07-99421e43a2f1@brocade.com> <49fe8cc5-0f0f-6cac-7a5c-803e81f5667d@runbox.com> Cc: "Charles (Chas) Williams" , Thomas Gleixner , Sebastian Andrzej Siewior , "x86@kernel.org" , LKML , Peter Zijlstra , Borislav Petkov , David Vrabel , Juergen Gross Message-ID: Date: Sun, 13 Nov 2016 01:05:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/2016 06:31 PM, Boris Ostrovsky wrote: > On 11/10/2016 10:05 AM, Charles (Chas) Williams wrote: >> >> >> On 11/10/2016 09:02 AM, Boris Ostrovsky wrote: >>> On 11/10/2016 06:13 AM, Thomas Gleixner wrote: >>>> On Thu, 10 Nov 2016, M. Vefa Bicakci wrote: >>>> >>>>> I have found that your patch unfortunately does not improve the >>>>> situation >>>>> for me. Here is an excerpt obtained from the dmesg of a kernel >>>>> compiled >>>>> with this patch *as well as* Sebastian's patch: >>>>> [ 0.002561] CPU: Physical Processor ID: 0 >>>>> [ 0.002566] CPU: Processor Core ID: 0 >>>>> [ 0.002572] [Firmware Bug]: CPU0: APIC id mismatch. Firmware: >>>>> ffff CPUID: 2 >>>> So apic->cpu_present_to_apicid() gives us a completely bogus APIC id >>>> which >>>> translates to a bogus package id. And looking at the XEN code: >>>> >>>> xen_pv_apic.cpu_present_to_apicid = xen_cpu_present_to_apicid, >>>> >>>> and xen_cpu_present_to_apicid does: >>>> >>>> static int xen_cpu_present_to_apicid(int cpu) >>>> { >>>> if (cpu_present(cpu)) >>>> return xen_get_apic_id(xen_apic_read(APIC_ID)); >>>> else >>>> return BAD_APICID; >>>> } >>>> >>>> So independent of which present CPU we query we get just some random >>>> information, in the above case we get BAD_APICID from >>>> xen_apic_read() not >>>> from the else path as this CPU _IS_ present. >>>> >>>> What's so wrong with storing the fricking firmware supplied APICid as >>>> everybody else does and report it back when queried? >>> >>> By firmware you mean ACPI? It is most likely not available to PV guests. >>> How about returning cpu_data(cpu).initial_apicid? >>> >>> And what was the original problem? >> >> The original issue I found was that VMware was returning a different set >> of APIC id's in the ACPI tables than what it advertised on the CPU's. >> >> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1266716.html > > For Xen, we recently added a6a198bc60e6 ("xen/x86: Update topology map > for PV VCPUs") to at least temporarily work around some topology map > problems that PV guests have with RAPL (which I think is what Vefa's > problem was). Hello Boris, (Sorry for the delay!) It appears that the problem is a bit different compared to the one corrected by a6a198bc60e6, because my kernel tree -- based on 4.8.6 -- already includes the -stable backport of that commit, i.e. 88540ad0820ddfb05626e0136c0e5a79cea85fd1 The patch I included in my previous e-mail (dated 2016-11-10) corrects root cause of the issue I am having with 4.8.6. Sebastian's original patch adding error checking to the RAPL module prevents the RAPL module from causing a kernel oops without my patch. The issue I am experiencing is caused by the boot-up code in the 'init_apic_mappings' function switching the APIC ops structure from Xen's structure to a no-op structure by calling the 'apic_disable' function. Please let me know if I can clarify or elaborate. For the record, using 4.8.7 without my correction patch patch does not rectify the issue at hand. 4.8.7 changes the call site of the 'init_apic_mapping' function, so I had thought that it could be helpful. Thank you, Vefa