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Re: [Xen-devel] [RFH] xen domain0 failover stuff

* Don Zickus (dzickus@xxxxxxxxxx) wrote:
> Continuing on my project to get a domain0 to failover to a second domain0,
> I have stumbled upon an out of memory problem.  Does anyone know what type
> of quirky scenario I would have had to create in order to have
> xen_create_contiguous_region() fail within
> swiotlb_init_with_default_size() of the linux x86_64 kernel?  

Sounds like nothing other than running low on that amount of contiguous


Typing that should show you what's available, I suspect it's less than
the swiotlb is asking for.

> I have managed to debug it down to alloc_heap_pages(MEMZONE_DMADOM, order)
> returning NULL.  But my problem is I couldn't figure out how those heaps
> were created in the first place.  

Boot time, IIRC.

> This domain is supposed to be configured with 256MB of memory (and "xm
> list" confirms that).  So for the actual domain to run out of memory seems
> illogical.  

It's the swiotlb asking for too large an order allocation.  You can
certainly limit it to smth small like 1MB (swiotlb=1 on dom0 kernel
command line) and hope that's sufficient.  Hmm, wonder if there would
be a way to reuse those pages from the first dom0.


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