WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

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


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel