场景描述：需要对整个系统的IO进行重新的部署

When performing a lot of I/O, the Xen dom0 kernel crashes with the 

following error:

[  325.437727] console [netcon0] enabled

[  325.437795] netconsole: network logging started

[ 1076.017245] mpt2sas 0000:03:00.0: DMA: Out of SW-IOMMU space for 

32768 bytes.

[ 1076.017333] BUG: unable to handle kernel NULL pointer dereference at 

0000000000000010

[ 1076.017517] IP: [<ffffffffa00668d8>] _scsih_qcmd+0x408/0x4d4 [mpt2sas]

[ 1076.017618] PGD b169067 PUD 1b85a067 PMD 0

[ 1076.017766] Oops: 0000 [#1] SMP

[ 1076.017891] last sysfs file: /sys/module/configfs/refcnt

[ 1076.017945] CPU 2

[ 1076.018023] Modules linked in: netconsole configfs xen_evtchn xenfs 

DMA: Out of SW-IOMMU space