From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:52704 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbbJCOgd (ORCPT ); Sat, 3 Oct 2015 10:36:33 -0400 Date: Sat, 3 Oct 2015 09:36:30 -0500 From: Bjorn Helgaas To: Christian Melki Cc: linux-pci@vger.kernel.org, Konrad Rzeszutek Wilk , Joerg Roedel , iommu@lists.linux-foundation.org Subject: Re: Fwd: SWIOTLB on 32-bit PAE. Message-ID: <20151003143630.GB17684@localhost> References: <560E9007.1000604@t2data.com> <560E92A0.9030707@t2data.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <560E92A0.9030707@t2data.com> Sender: linux-pci-owner@vger.kernel.org List-ID: [+cc Konrad, Joerg, iommu list] On Fri, Oct 02, 2015 at 04:20:16PM +0200, Christian Melki wrote: > I discovered a strange error on my machine. 32-bit PAE 4.2.0 without > IOMMU code (yeah, I know). > When writing to an ext4 filesystem on a USB disk my kernel would hang > and not return control to userspace. It would spew kernel messages to > syslog as fast as it could without giving userspace any time, ie "hang" > as far as a user sees it. The device itself is ok and the filesystem is > clean. > I get messages like this, millions of them. > > Oct 2 14:33:06 voodoochild kernel: [ 223.287447] nommu_map_sg: > overflow 25dcac000+1024 of device mask ffffffff > Oct 2 14:33:06 voodoochild kernel: [ 223.287448] nommu_map_sg: > overflow 25dcac000+1024 of device mask ffffffff > Oct 2 14:33:06 voodoochild kernel: [ 223.287449] nommu_map_sg: > overflow 25dcac000+1024 of device mask ffffffff > > I disovered that SWIOTLB was not on. It is only provided for 64-bit > machines where it is default. On 32-bit SWIOTLB seems disabled > unless you are running with some IOMMU/AGPGART code. > > But what about 32-bit PAE? Would that not qualify for SWIOTLB without IOMMU? > > I am a novice in this area. Maybe this is a Kconfig "bug" for us > that like to hang ourselves with CONFIG_* rope? :) I'd like to think > that SWIOTLB should be default for 32-bit PAE too? > > Best regards, > Christian > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html