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Re: [Xen-devel] [PATCH] x86: fix variable_test_bit()asmconstraints

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] x86: fix variable_test_bit()asmconstraints
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Sun, 16 Mar 2008 14:08:46 +0000
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On 14/3/08 17:08, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> Actually, just trying it out with set_bit() results in a number of cases
>> where the field used is neither 32- nor 64-bit. The very first one I
>> looked at even has only a byte-aligned (leaving out internal knowledge
>> of the allocator) allocation that it accesses (domid_bitmap in
>> xen/drivers/passthrough/vtd/iommu.c).
> 
> How did you find that one? It's void* so I would have thought you'd miss that
> one as the compiler will happily cast void*. I hope there aren't too many
> lurkers like that! Perhaps you were trying to do your automatic field-width
> detection approach. I think that's not needed, but it would conveniently find
> these void* callers. Perhaps we should wrap the bitops in a macro that will
> fail on void*?
> 
> I'm happy to do this change (void* -> long*) myself, by the way, as it's the
> kind of thing that's as much work to review as it is to do in the first place.

Done, as changeset 17194.

 -- Keir



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