From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laura Abbott Subject: Re: Warning from AMD IOMMU performance counters Date: Mon, 22 Feb 2016 17:36:09 -0800 Message-ID: <56CBB789.4020704@redhat.com> References: <56C798B8.6080009@redhat.com> <56CA69C7.3050508@iommu.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <56CA69C7.3050508-6ukY98dZOFrYtjvyW6yDsg@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Wan Zongshun , Joerg Roedel , Suravee.Suthikulpanit-5C7GfCeVMHo@public.gmane.org Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Linux Kernel Mailing List List-Id: iommu@lists.linux-foundation.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