On 01/27/2016 10:56 PM, David Miller wrote:
From: tndave <tushar.n.d...@oracle.com>
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?
People get overzealoud with __packed.
And even if it doesn't cause unaligned accesses like this, it generates
terrible code (byte at a time accesses to words) on several architectures.
True. For the same reason I want to clarify if __packed is actually
needed? instead of fixing it with get_unaligned/put_unaligned()!
-Tushar
