netdev - Re: [Bugme-new] [Bug 10790] New: driver "sunhme" experiences corrupt packets if machine has more than 2GB of memory

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Date:	Wed, 4 Jun 2008 10:21:21 +0200
From:	Karsten Keil <kkeil@...e.de>
To:	David Miller <davem@...emloft.net>
Cc:	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	bugme-daemon@...zilla.kernel.org, f0h3a-kernel@...oo.com,
	kkeil@...e.de
Subject: Re: [Bugme-new] [Bug 10790] New: driver "sunhme" experiences corrupt packets if machine has more than 2GB of memory

On Tue, Jun 03, 2008 at 04:33:17PM -0700, David Miller wrote:
> From: Andrew Morton <akpm@...ux-foundation.org>
> Date: Sun, 25 May 2008 11:45:48 -0700
> 
> > Note that this patch from Karsten:
> > https://bugzilla.novell.com/attachment.cgi?id=217968 did not work.
> 
> That patch is unlikely to be the issue, right.
> 

No, this patch was a experiment to fix the issue, it is not in our kernel
by default.

> > Stoopid question: if it fails at 2GB, should we try DMA_31BIT_MASK?
> 
> I've scoured all of the docs and the chip itself and the PCI front-end
> it is connected to support full 32-bit PCI addressing.
> 
> The bug report says platform "All" but the report specifically
> mentions Q6600 cpus, is this x86_64 by chance?  I wonder if the
> problem is that we use GFP_ATOMIC/GFP_KERNEL for allocations
> of SKB data, and we end up with buffers above 4GB but the IOMMU
> mapping operation doesn't cope with that correctly.

Yes it is x86_64 and I think, that if you put more as 2G in this machine,
some physical addresses are behind the 4 GB border.


> 
> In the arch/x86/kernel/pci-nommu.c case, this would result in
> kernel log messages from check_addr():
> 
> 		if (*hwdev->dma_mask >= DMA_32BIT_MASK)
> 			printk(KERN_ERR
> 			    "nommu_%s: overflow %Lx+%zu of device mask %Lx\n",
> 				name, (long long)bus, size,
> 				(long long)*hwdev->dma_mask);

-- 
Karsten Keil
SuSE Labs
ISDN and VOIP development
SUSE LINUX Products GmbH, Maxfeldstr.5 90409 Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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