[Xen-devel] x86-64 32bit applications support discussion

[Jerone Young <jyoung5@xxxxxxxxxx>]

        This thread is intended for discussion of 32bit application support
under x86-64 virtual domains. To all reading this is for development
purposes (x86-64 support is not done yet).
        
        I've been actively looking into 32bit application support for the
x86-64 Virutal Domains. I do have a question that I wanted to bring to
the list to start the discussion.

        Since the virtual domain & applications are all running in ring 3. Does
the hypervisor need to know how to tell the CPU when and when not to go
into compatibility mode to  run running 32bit applications properly
under virtual domains? As you may know while under Long mode you have
two sub modes: 64-bit mode & compatibility (for 32bit stuff). The
problem I see is that since we are in Long Mode the virutal domain needs
to tell CPU to go into the sub mode compatibility mode for it's 32
applications but does not have the access to do so. I'm not sure the
best way of going about this (new hypercall?) ?
        

-- 
Jerone Young
IBM Linux Technology Center
jyoung5@xxxxxxxxxx
512-838-1157 (T/L: 678-1157)



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