From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laura Abbott Subject: Warning from AMD IOMMU performance counters Date: Fri, 19 Feb 2016 14:35:36 -0800 Message-ID: <56C798B8.6080009@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Joerg Roedel Cc: iommu@lists.linux-foundation.org, Linux Kernel Mailing List List-Id: iommu@lists.linux-foundation.org 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? Thanks, Laura