CONFIG_ARM_DMA_IOMMU_ALIGNMENT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Maximum PAGE_SIZE order of alignment for DMA IOMMU buffers


Linux Kernel Configuration
└─>Maximum PAGE_SIZE order of alignment for DMA IOMMU buffers
In linux kernel since version 3.1 (release Date: 2011-10-24)  
DMA mapping framework by default aligns all buffers to the smallest
PAGE_SIZE order which is greater than or equal to the requested buffer
size. This works well for buffers up to a few hundreds kilobytes, but
for larger buffers it just a waste of address space. Drivers which has
relatively small addressing window (like 64Mib) might run out of
virtual space with just a few allocations.

With this parameter you can specify the maximum PAGE_SIZE order for
DMA IOMMU buffers. Larger buffers will be aligned only to this
specified order. The order is expressed as a power of two multiplied
by the PAGE_SIZE.