On Tue, 2013-07-30 at 14:34 -0500, Rob Herring wrote:

I can think of lots of ways it would be cleaner, but that is not what
ARM defined. There are 3 cases to handle: 32-bit only calls, 64-bit only
calls and both 32/64-bit calls. I think hypervisors have the same issue
as firmware. Do you know the guest is 32 or 64 bit up front and can
provide it a dtb based on that?

Yes. An EL cannot change its own bit width and needs to rely on the EL
above returning in the right mode. IOW a hypervisor needs to know if it
is launching a 32- or 64-bit guest already.

I suppose in theory we could supply a mode switch hypercall, but we
don't and I think that is rather out of scope here...

Ian.