Subject: i40e: Kernel unaligned access due to 'struct i40e_dma_mem' being 'packed'

From: tndave <[email-masked]>
Date: Wed, 27 Jan 2016 17:50:14 -0800

Hi,

i40e driver has 'struct i40e_dma_mem' defined with 'packed' directive
causing kernel unaligned errors on sparc (when 40e_allocate_dma_mem_d()
is being called)

log_unaligned: 1031 callbacks suppressed
Kernel unaligned access at TPC[448ae8] dma_4v_alloc_coherent+0x188/0x2e0
Kernel unaligned access at TPC[448ae8] dma_4v_alloc_coherent+0x188/0x2e0
Kernel unaligned access at TPC[448ae8] dma_4v_alloc_coherent+0x188/0x2e0
Kernel unaligned access at TPC[448ae8] dma_4v_alloc_coherent+0x188/0x2e0

This can be fixed with get_unaligned/put_unaligned(). However I don't
see 'struct i40e_dma_mem' is being directly shoved into NIC hardware.
But instead fields of the struct are being read and used for hardware
(e.g. dma_addr_t pa). For the test, I remove __packed, and i40e driver
and HW works fine. (of course kernel unaligned errors are gone too).
My question is, does 'struct i40e_dma_mem' required to be __packed?

Thanks.

-Tushar