The output buffer in test_ahash_speed will point to an address located
within the tcrypt module image.
This causes problems when trying to DMA map the buffer.
For e.g. on ARM-based LS1021A, a page fault occurs within the
DMA API when trying to access the struct page returned by
virt_to_page(output):

insmod tcrypt.ko mode=403

testing speed of async sha1 (sha1-caam)
test  0 (   16 byte blocks,   16 bytes per update,   1 updates):
Unable to handle kernel paging request at virtual address f07e9080
pgd = e58d0e00
[f07e9080] *pgd=80000080007003, *pmd=00000000
Internal error: Oops: 206 [#1] SMP THUMB2
Modules linked in: tcrypt(+)
CPU: 1 PID: 1119 Comm: insmod Not tainted 4.2.0-rc1-256134-gbf433416e675 #1
Hardware name: Freescale LS1021A
task: ea063900 ti: e5a34000 task.ti: e5a34000
PC is at dma_cache_maint_page+0x38/0xd0
LR is at __dma_page_cpu_to_dev+0x15/0x64
pc : [<800155a0>]    lr : [<8001564d>]    psr: 000f0033
sp : e5a35ca0  ip : 8063df00  fp : f...