[dpdk-dev] [PATCH] eal: fix 64bit address alignment in 32-bit builds

[Thomas Monjalon]

28/04/2017 10:15, Bruce Richardson:
> On i686 builds, the uint64_t type is 64-bits in size but is aligned to
> 32-bits only. This causes mbuf fields for rearm_data to not be 16-byte
> aligned on 32-bit builds, which causes errors with some vector PMDs which
> expect the rearm data to be aligned as on 64-bit.
> 
> Given that we cannot use the extra space in the data structures anyway, as
> it's already used on 64-bit builds, we can just force alignment of physical
> address structure members to 8-bytes in all cases. This has no effect on
> 64-bit systems, but fixes the updated PMDs on 32-bit.

I agree to align on 64-bit in mbuf.

> Fixes: f4356d7ca168 ("net/i40e: eliminate mbuf write on rearm")
> Fixes: f160666a1073 ("net/ixgbe: eliminate mbuf write on rearm")
[...]
> --- a/lib/librte_eal/common/include/rte_memory.h
> +++ b/lib/librte_eal/common/include/rte_memory.h
> -typedef uint64_t phys_addr_t; /**< Physical address definition. */
> +/** Physical address definition. */
> +typedef uint64_t phys_addr_t __rte_aligned(sizeof(uint64_t));

Why setting this constraint for everyone?