linux-kernel - Re: kernel BUG at drivers/scsi/aic7xxx/aic79xx

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Date:	Sun, 09 Mar 2008 18:31:18 +0300
From:	Michael Tokarev <mjt@....msk.ru>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	FUJITA Tomonori <tomof@....org>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, fujita.tomonori@....ntt.co.jp
Subject: Re: kernel BUG at drivers/scsi/aic7xxx/aic79xx_osm.c:1490!

James Bottomley wrote:
> On Sun, 2008-03-09 at 21:29 +0900, FUJITA Tomonori wrote:
>> On Sun, 09 Mar 2008 14:23:13 +0300
>> Michael Tokarev <mjt@....msk.ru> wrote:
>>
>>> Just got quite.. bad situation on a production server
>>> here.  The machine locked up hard several times in a
>>> row (required hard reboot).  So I finally enabled watchdog
>>> subsystem which helped.
>>>
>>> Now I see the following (over netconsole):
>>>
>>> DMA: Out of SW-IOMMU space for 65536 bytes at device 0000:08:07.0
>>> ------------[ cut here ]------------
>>> kernel BUG at drivers/scsi/aic7xxx/aic79xx_osm.c:1490!
>> Seems that you was out of swiommu space (and aic79xx can't handle it
>> though it should). This happened because:
>>
>> a) you produced more I/Os than swiommu can handle.
>>
>> b) swiommu space leaks due to bugs.
>>
>> If you hit this problem due to a), the following boot option might
>> help:
>>
>> swiotlb=65536

Running with this parameter now - no lockups so far.

> Actually, it's worse than this.  The aic79xx is a fully 64 bit capable
> PCI card, it shouldn't be using the iommu at all.  However, it has three
> DMA modes:  64 bit, 39 bit and 32 bit; with a corresponding resource
> cost increasing with the number of bits.  It employs special APIs to
> size the masks according to the memory, in aic79xx_osm_pci.c:
[]
> Could you firstly tell me how much memory you have, and secondly
> instrument this code with the patch below to see if we can work out what
> it's doing?

The memory map is below (6Gb total).  The patch - kernel is being compiled
right now.

Linux version 2.6.24-x86-64 (mjt@...tus.tls.msk.ru) (gcc version 4.2.3 20071123 (prerelease) (Debian 4.2.2-4)) #2.6.24.2 SMP Mon Feb 18 16:04:41 MSK 2008
Command line: auto BOOT_IMAGE=linux-test ro root=100 swiotlb=65536 panic=30 elevator=deadline
BIOS-provided physical RAM map:
  BIOS-e820: 0000000000000000 - 000000000009dc00 (usable)
  BIOS-e820: 000000000009dc00 - 00000000000a0000 (reserved)
  BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
  BIOS-e820: 0000000000100000 - 00000000cfffca00 (usable)
  BIOS-e820: 00000000cfffca00 - 00000000d0000000 (ACPI data)
  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
  BIOS-e820: 0000000100000000 - 00000001b0000000 (usable)


/mjt
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