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Re: [Xen-ia64-devel] I cannot create domU anymore

To: Tristan Gingold <tgingold@xxxxxxx>
Subject: Re: [Xen-ia64-devel] I cannot create domU anymore
From: Alex Williamson <alex.williamson@xxxxxx>
Date: Sun, 17 Jun 2007 08:43:37 -0600
Cc: Xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
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On Sun, 2007-06-17 at 07:59 +0200, Tristan Gingold wrote:
> Hi,
> Using tip, everything recompiled and installed I can't create domU anymore:
> the domU kernel fails early:
> Kernel panic - not syncing: Failed to setup Xen contiguous region
>  <1>Unable to handle kernel NULL pointer dereference (address 
> 0000000000000000)
> swapper[0]: Oops 11012296146944 [1]
> Modules linked in:
> Pid: 0, CPU 0, comm:              swapper
> psr : 00001210084a2010 ifs : 8000000000000308 ip  : [<a00000010012ba61>]    
> Not tainted
> ip is at kmem_cache_alloc+0x101/0x2a0
> unat: 0000000000000000 pfs : 8000000000000712 rsc : 000000000000000b
> rnat: 0000000000000000 bsps: 0000000000000000 pr  : 0000000000009949
> ldrs: 0000000000000000 ccv : 0000000000000000 fpsr: 0009804c8a70433f
> csd : 0000000000000000 ssd : 0000000000000000
> b0  : a000000100049b10 b6  : a000000100934340 b7  : a00000010004a920
> Any tip ?

   That's coming from the swiotlb code.  By default a domU will use the
xen machine vector, which relies on xen_dma instead of swiotlb for DMA.
However, if you boot a domU with machvec=dig it will make use of the
swiotlb.  This works for me, but is really only useful if you're running
driver domains with 32bit devices, which isn't really recommended.
Could that be the case?  Unfortunately there's a limited amount of
memory below 4G for xen to remap.  Maybe the default size of the swiotlb
should be smaller if running in a domU?  Thanks,


Alex Williamson                             HP Open Source & Linux Org.

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