Bug#603727: i386 Dom0 crashes after doing some I/O on local storage
reassign 603727 linux-2.6
retitle 603727 Out of SW-IOMMU space with mpt2sas on Xen
A bit of googling seems to suggest that mptsas is a particularly heavy
user of swiotlb. It might be interesting to try with a large swiotlb,
i.e. by adding swiotlb=32768 to your kernel (not hypervisor) command
line. I think the units are pages and the default is 64M, so trying 128M
might be useful.
Also you should ensure you are using the latest kernel or even perhaps
the kernel + hypervisor from Wheezy.