Re: [Xen-devel] [PATCH 4/5] xen: introduce XEN_GUEST_HANDLE_PARAM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-08-07 at 14:08 +0100, Jan Beulich wrote:
> See how
> x86-64 just recently got the ILP32 model [aka x32] added for
> this very reason.)

For userspace only though, with the kernel remaining a full 64-bit
kernel. I don't know what direction they eventually took but there was
also a contingent in favour of using the 64-bit syscall ABI for x32.

I don't think that the wastage at the hypercall interface is going to be
significant. Especially once you consider that many of the 32-bit fields
actually need to be 64-bit for a compat mode guest any, e.g. MFNs should
certainly be 64 bit regardless or else you impose limitations on 32-bit
guests which the 64-bit hypervisor doesn't itself have.

Ian.


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