Re: [Xen-devel] [PATCH 02/18] PVH xen: add XENMEM_add_to_physmap_range

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-05-31 at 11:14 +0100, Jan Beulich wrote:
> All I'm asking is, instead of introducing a new function parameter
> here, to use an otherwise unused field of the xatp input
> structure. This is based on the fact that the field is being
> evaluated once directly in arch_memory_op(), and then no longer
> needed.

Ah ok, yes, that sounds ok.

Although I'm not convinced the compiler wouldn't do the smart thing
either way. Since the arguments are passed in registers it might even
hurt by hitting memory instead of just using the value held in the
register (realistically it will be a warm cache line, so probably
doesn't matter).

Would need care to make sure that this reuse didn't leak into the
hypercall ABI and end up painting ourselves into a corner WRT using all
three domains in the future, should it come to it.

Ian.


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