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SubjectRe: Error: DMA: Out of SW-IOMMU space [was: External USB drives become unresponsive after few hours.]
On Thu, Apr 16, 2015 at 06:57:46PM +0200, Dorian Gray wrote:
> On 16 April 2015 at 16:15, Alan Stern <> wrote:
> > This appears to be a problem with the IOMMU or SWIOTLB subsystems, not
> > the USB subsystem. I have CC'ed the appropriate mailing lists.
> Thanks, I'm far from being a kernel expert, so was expecting it could
> be wrong subsection.
> On 16 April 2015 at 16:24, Suman Tripathi <> wrote:
> > Try increasing the SWIOTLB size to 128MB .Default is 64MB.
> Ok, so I'm back to k3.18.7 (default in the latest Fatdog), although
> I'm not sure what should be the exact value of swiotlb boot param?
> Got totally mixed results from uncle Google - some says the unit is in
> MiB, some that it's 4k pages and another that 128MiB = 65536, so I
> played it safe and used swiotlb=131072.
> Is this correct?
> It may take a few days, but I'll let you know if it worked (or for how
> long, if not).
> On 16 April 2015 at 16:54, Alexander Duyck <> wrote:
> > More likely would be a device driver that is DMA mapping memory but not
> > unmapping it after it is done resulting in the bounce buffer pool being
> > depleted.
> > You might want dump the list of drivers loaded on the system with lsmod,
> > and then possibly look at doing a git bisect for something introduced
> > between 3.17 and 3.18 since that seems to be when you started seeing
> > this issue.
> Ok, I'll (try to) look at this, but like I said - I'm not a kernel
> (nor git) expert.
> Anyway, I guess I'm gonna start with this:
> Who knows...perhaps I'll find something...

And easier way is to compile the kernel with CONFIG_DMA_API_DEBUG
and then load the attached module.

That should tell you who and what else is holding on the buffers.

> Thank you all for the replies.
> Jake
> _______________________________________________
> iommu mailing list
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License v2.0 as published by
* the Free Software Foundation
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.

#include <linux/module.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/stat.h>
#include <linux/err.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/limits.h>
#include <linux/device.h>
#include <linux/pci.h>
#include <linux/blkdev.h>
#include <linux/device.h>

#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/highmem.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/blkpg.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/mount.h>
#include <linux/uio.h>
#include <linux/namei.h>
#include <asm/uaccess.h>

#include <linux/pagemap.h>
#include <linux/pagevec.h>

#include <linux/dma-debug.h>

#define DUMP_DMA_FUN "0.1"

MODULE_AUTHOR("Konrad Rzeszutek Wilk <konrad@virtualiron>");

static int __init dump_dma_init(void)
return 0;

static void __exit dump_dma_exit(void)

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