Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934761AbcKMSDa convert rfc822-to-8bit (ORCPT ); Sun, 13 Nov 2016 13:03:30 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:27186 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934067AbcKMSD2 (ORCPT ); Sun, 13 Nov 2016 13:03:28 -0500 Subject: Re: [PATCH] x86/cpuid: Deal with broken firmware once more To: "M. Vefa Bicakci" 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 , xen-devel From: Boris Ostrovsky Message-ID: <68840c0b-44c9-ddd8-bfab-f4fd8bacbaf0@oracle.com> Date: Sun, 13 Nov 2016 13:04:36 -0500 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: 8BIT X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3713 Lines: 93 On 11/12/2016 05:05 PM, M. Vefa Bicakci wrote: > 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. I don't see any messages from you on that date. Can you provide a link to it (and to Sebastian's patch)? (BTW, generally it's a good idea to copy xen-devel list on any Xen-related issues). > > 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. apic_disable() is only invoked if there is no APIC present (i.e. detect_init_APIC() returns a non-zero value) and I don't think this can happen. Is your CPUID[1].edx[9] not set? -boris > > 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