From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755419Ab3BEN51 (ORCPT ); Tue, 5 Feb 2013 08:57:27 -0500 Received: from mail-la0-f50.google.com ([209.85.215.50]:49679 "EHLO mail-la0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754018Ab3BEN5Y (ORCPT ); Tue, 5 Feb 2013 08:57:24 -0500 MIME-Version: 1.0 In-Reply-To: <20130205133104.GC2532@8bytes.org> References: <1359657210.6061.3.camel@lorien2> <20130201130035.GE25591@8bytes.org> <1359743519.2759.38.camel@lorien2> <20130205133104.GC2532@8bytes.org> Date: Tue, 5 Feb 2013 06:57:21 -0700 Message-ID: Subject: Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4 From: Shuah Khan To: Joerg Roedel Cc: Shuah Khan , LKML , stable , iommu@lists.linux-foundation.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 5, 2013 at 6:31 AM, Joerg Roedel wrote: > Hi Shuah, > > On Fri, Feb 01, 2013 at 11:31:59AM -0700, Shuah Khan wrote: >> Yes, 3.7 has the same window of opportunity for this race condition, >> however I couldn't figure out why it doesn't happen on 3.7. On 3.7 the >> window between amd_iommu_init_hardware() and amd_iommu_init_dma_ops() >> might actually be wider than the window in 3.4. > > I think this is highly timing related. IOMMU initialization may have > been moved by a few milliseconds between the kernel versions which might > cause the warnings to appear or disappear. I don't think it has much > value to dive deeper into the differences between the initialization > sequences. > > As somethimes with such issues there is a simple and a more complex fix > for that. I'll try to come up with a simple fix for the next merge > window and implement the clean and more complex one for the next one. > Hi Joerg, Thanks much. I will hang on to this test system for testing your fix. -- Shuah