From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756881AbcBWBgT (ORCPT ); Mon, 22 Feb 2016 20:36:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37469 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756755AbcBWBgP (ORCPT ); Mon, 22 Feb 2016 20:36:15 -0500 Subject: Re: Warning from AMD IOMMU performance counters To: Wan Zongshun , Joerg Roedel , Suravee.Suthikulpanit@amd.com References: <56C798B8.6080009@redhat.com> <56CA69C7.3050508@iommu.org> Cc: iommu@lists.linux-foundation.org, Linux Kernel Mailing List From: Laura Abbott Message-ID: <56CBB789.4020704@redhat.com> Date: Mon, 22 Feb 2016 17:36:09 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <56CA69C7.3050508@iommu.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/21/2016 05:52 PM, Wan Zongshun wrote: > > > -------- Original Message -------- >> Hi, >> >> Since about 4.4, we've been seeing reports of this warning on every boot >> from some users: >> >> WARNING: CPU: 2 PID: 1 at drivers/iommu/amd_iommu_init.c:2301 >> amd_iommu_pc_get_set_reg_val+0xa8/0xe0() >> Modules linked in: >> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.2-300.fc23.x86_64 #1 >> Hardware name: Hewlett-Packard HP EliteBook 755 G2/221C, BIOS M84 Ver. >> 01.10 10/20/2015 >> 0000000000000000 0000000026124b43 ffff88042d687d20 ffffffff813b0c9f >> 0000000000000000 ffff88042d687d58 ffffffff810a2f12 ffff88042f014800 >> 0000000000000040 0000000000000000 ffffffff81d6c73d 0000000000000000 >> Call Trace: >> [] dump_stack+0x44/0x55 >> [] warn_slowpath_common+0x82/0xc0 >> [] ? memblock_find_dma_reserve+0x16a/0x16a >> [] warn_slowpath_null+0x1a/0x20 >> [] amd_iommu_pc_get_set_reg_val+0xa8/0xe0 >> [] iommu_go_to_state+0x4d6/0x1384 >> [] ? kvasprintf+0x7a/0xa0 >> [] ? memblock_find_dma_reserve+0x16a/0x16a >> [] amd_iommu_init+0x13/0x201 >> [] pci_iommu_init+0x12/0x3c >> [] do_one_initcall+0xb3/0x200 >> [] ? parse_args+0x295/0x4b0 >> [] kernel_init_freeable+0x189/0x223 >> [] ? rest_init+0x80/0x80 >> [] kernel_init+0xe/0xe0 >> [] ret_from_fork+0x3f/0x70 >> [] ? rest_init+0x80/0x80 >> >> Full bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=1310258 >> >> Any idea what might be causing this spew? > > I also see this warning. > > Suravee's the one of this patch series might be fix this issue, you can try it. > > [PATCH V4 0/6] perf/amd/iommu: Enable multi-IOMMU support > > That patch had other dependencies. I brought what I thought were enough of them in to at least compile for the reporter to test (perf_event changes from Borislav Petkov). Apparently the kernel doesn't boot with the series so suspect there is an integration issue somewhere. I'm going to see if I can more information from the reporter about what exactly went wrong to see if I need more dependencies. It would be nice to get a single patch which could be applied to stable. Tainting the kernel immediately on bootup makes sorting through problems more difficult. Thanks, Laura