[Xen-devel] RFC: 32 bits as smallest atomic size.

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

In PPC land we have an issue where cmpxchg operations can only be
applied to strictly aligned 32 and 64 bit quantities.

We understand on x86 the use of the packed attribute has certain
benefits, but in the common areas we believe that portability should
be the primary concern in the common code.

I can only assume that much debate will come from this as we find
alignment and size issues all over.

The particular offender at the moment is:
  include/public/grant_table.h flags 76 u16 flags;

It is used with atomic methods such as cmpxchg_user() and clear_bit().

Any thoughts on how to proceed with this would be appreciated.

-JX

BTW: is clear_bit() as implemeted for x86 have soem alignment issues?
My expertise in this space is limited.





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