From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933657Ab0CMDJr (ORCPT ); Fri, 12 Mar 2010 22:09:47 -0500 Received: from mga07.intel.com ([143.182.124.22]:21365 "EHLO azsmga101.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757945Ab0CMDJn (ORCPT ); Fri, 12 Mar 2010 22:09:43 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,629,1262592000"; d="scan'208";a="254220832" Message-ID: <4B9B01F5.3000807@linux.intel.com> Date: Fri, 12 Mar 2010 19:09:41 -0800 From: Andi Kleen User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: akataria@vmware.com CC: Len Brown , the arch/x86 maintainers , linux-acpi , LKML , Petr Vandrovec Subject: Re: swiotlb detection should be memory hotplug aware ? References: <1268446032.13691.69.camel@ank32> In-Reply-To: <1268446032.13691.69.camel@ank32> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org , Alok Kataria wrote: Hi Alok, > Hi, > > Looking at the current code swiotlb is initialized for 64bit kernels > only when the max_pfn value is greater than 4G (MAX_DMA32_PFN value). > So in cases when the initial memory is less than 4GB the kernel boots > without enabling swiotlb, when we hotadd memory to such a kernel and go > beyond the 4G limit, swiotlb is still disabled. As a result when any > 32bit devices start using this newly added memory beyond 4G, the kernel > starts spitting error messages like below or in some cases it causes > kernel panics. Yes seems like a real problem. > > 1. Enable swiotlb for all 64bit kernels which have memory hot-add > support. I don't think that's a good idea. It would enable it everywhere on distributions which compile with hotadd. Need (2) > 2. Instead of checking the max_pfn value in pci_swiotlb_detect, check > for max_hotpluggable_pfn (or some such) value. Though I don't see such a > value readily available. I could parse the SRAT and get hotplug memory > information but that will make swiotlb detection logic a little too > complex. A quick look around srat_xx.c files and the acpi_memhotplug > module didn't find any useful API that could be used directly either. > So was wondering if any of you are aware of an easy way to get such > information ? I have a patchkit to revamp the SRAT parsing to store the hotadd information more efficiently (the current way is pretty dumb) I need to repost that. With that it would be relatively easy to do I think. -Andi