[Xen-devel] Re: __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling for fast paths

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

>From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
>       
>       While browsing the code, I noticed this in xmalloc.c:
>
>#ifndef __ia64__
>    BUG_ON(align > SMP_CACHE_BYTES);
>#endif
>
>       This is clearly wrong: due to header alignment we cannot give
you a
>greater alignment than SMP_CACHE_BYTES.  Overriding this will cause the
>allocation to succeed, but not give the alignment requested.  It
usually
>indicates the caller should be fixed.
>
>Does someone with an ia64 box know why, or want to rip it out and see
>what breaks?

The BUG_ON gets triggered on Xen/ia64.  IIRC, there is some
subtle semantic difference between how this constant is
used on Xen/x86 and Linux/ia64 (from whence the Xen/ia64
header file is directly leveraged).

Matt, do you recall the results of your investigation
into this?

Dan

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