Re: [Qemu-devel] [PULL V3 00/20] Net patches

[Eric Blake <eblake@redhat.com>]

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On 05/26/2016 09:08 AM, Peter Maydell wrote:
> 
> Apologies for the lack of any backtraces in the output, but
> this is almost certainly the result of trying to do le64_to_cpu()
> or cpu_to_le64() on a buffer which isn't necessarily aligned
> (usually some pointer into guest memory). Use the functions
> ldq_le_p() and stq_le_p() instead, which will handle a
> potentially misaligned pointer for you. (There are similar
> functions for other access widths too.)

Since these functions are constructed by ## token pasting, it's very
hard to grep .h files to see what variations-on-a-theme are actually
available, nor is the documentation clear on what they all do (in-place
vs. copy, pass a value vs. a pointer, ...).  It might be a nice
bite-sized task to beef up the documentation and at least call out ALL
of the endian-conversion functions in a nice comment (to make it
greppable), along with this tidbit of information on which forms are
optimized but require alignment, vs. work anywhere but potentially slower.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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