From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Melki Subject: Re: Fwd: SWIOTLB on 32-bit PAE. Date: Mon, 5 Oct 2015 13:35:23 +0200 Message-ID: <5612607B.2050208@t2data.com> References: <560E9007.1000604@t2data.com> <560E92A0.9030707@t2data.com> <20151003143630.GB17684@localhost> <20151003180007.GA4732@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151003180007.GA4732-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@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: Konrad Rzeszutek Wilk , joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi. I think I rang the bell a bit early. The corruption is in grub legacy (I assumed that would be in Linux too, but it wasn't). The on disk format of ext4 apparently stores byte ordering somehow? I thought the on disk format of ext4 was a specific endian (little). Since only that file is unreadable in grub, but readable in Linux.. I am guessing endian issues somehow.. which still is strange. Regards, Christian On 10/03/2015 08:00 PM, Konrad Rzeszutek Wilk wrote: > On Sat, Oct 03, 2015 at 09:36:30AM -0500, Bjorn Helgaas wrote: >> [+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? > > It most certainly would! >>> >>> 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? > > Aye. I presume that you had done a small change already for this? > Would you be willing to post it on lkml and CC me ? > > Thank you. >>> >>> Best regards, >>> Christian >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-pci" in >>> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html