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xen-devel
Re: [Xen-devel] 32/64-bit hypercall interface
On 30 Sep 2005, at 01:54, Andrei Petrov wrote:
How about writing a script that converts the Xen public headers into a
set that, when compiled on 32-bit ppc, match the 64-bit ppc layout?
That might be saner than trying to manually finesse our headers around
the ppc abi so that building in 32-bit or 64-bit environment both
happen to give same binary layout.
If this type of ABI compatibility is needed, interface data structures
should be declared
platform-independantly, i.e using 'sized' types (yeah, field alignment
should be taken care of too).
That'll guarantee 32/64 bit independance and that's good thing to
have. Once defined it can be
managed in controlled way. There could be penalty involved for using
larger data types than neccessary,
but that can be resolved having 32-bit(or 64-bit, depending whichever
is attractive as basic)
hypercall subset.
When we previously had this, by defining packed structs, there were
plenty of screams that it wasn't ANSI compliant, and that performance
sucks on some architectures. At the time there seemed no good reason
for cross-ABI compatibility (we don't plan to stuff these structs into
network packets, for example).
-- Keir
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