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[Xen-users] Re: About swiotlb and " ...PCI-DMA: Out of SW-IOMMU..."error

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Subject: [Xen-users] Re: About swiotlb and " ...PCI-DMA: Out of SW-IOMMU..."error
From: Markus Schuster <ma.schuster@xxxxxx>
Date: Sun, 09 Dec 2007 03:31:36 +0100
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Shaun R. wrote:
> [..]
>  The only solution i've found to stopping this from happening is
> to force dom0 to use less than 2GB of ram.  In my case i forced my dom0 to
> use 1024MB of ram leaving the rest (around 15GB) on vacation.  
> I'm running 3ware 9560 controllers btw too if it matters.

I've had a discussion (subject: "Massive problems with 'PCI-DMA: Out of
SW-IOMMU space for XXX bytes [..]' with 3Ware controller") with Keir Fraser
on xen-devel this days because of this problem and for /me dom0 memory size
does not matter (I've tried to not restrict dom0 (so it can use almost all
of my 2GB) and to set it to only 128MB - no difference). 
btw: I own a 3ware 9500 - so we use the same driver - 3w_9xxx - maybe here
the problem starts...

Here is a quote from an e-mail Keir sent me off-list:

> Sounds like the 2.6.18 kernel is screwed then. Perhaps the
> 2.6.18 driver leaks swiotlb space... I haven't got many spare cycles right
> now to look into this. Probably the next step though might be to dump the
> swiotlb state when this bug-out happens, and see if the state looks like a
> leak has been happening. A leak makes sense given that you seem to run out
> of space eventually regardless of swiotlb size.

For what I can say for now is that it does not happen on my old 2.6.16
kernel patched for Xen 3.0.4. With a 2.6.18 patched for Xen 3.1.2 it
happens. Will do some additional tests this days (if time permits). 


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