Re: [Xen-devel] memop struct packing, 32/64 bits

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Jan 23, 2012 at 09:24:29AM +0000, Jan Beulich wrote:
> >>> On 22.01.12 at 21:37, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> wrote:
> > So for the "Fun" of it I tried to see if the 'struct
> > xen_processor_performance' has some 32/64-bit issues and was surprised
> > to find they do. What I am more surprised to find is that nobody seems
> > to have had any troubles with this as it seems to have been there since
> > it was initially implemented. The major issue would have been with the
> > 'shared_type', 'domain_info' and the pointer to the 'states' being at
> > different offsets (So when running a 32-bit dom0 with a 64-bit
> > hypervisor).
> 
> Are you having an actual problem with the layout differences, or
> did you just observe them? As Keir said, this is being dealt with
> inside the hypervisor - the (Dom0) kernel doesn't need to care at
> all (which was the primary requirement when the 32-on-64
> support got added).

I just observed them when I was trying to use memcpy on the Linux<->Xen
structs and saw some padding issues. The further I looked the more
I saw of it and was wondering why nobody had tripped over it.

But the compat layer that Keir pointed to me does fix the 32/64 bit
issue I observed - so wheew, no bugs!

Thanks!
> 
> Jan
> 
> 
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