PPC: Add asm helpers for BE 32bit load/store

From assembly code we might not only have to explicitly BE access 64bit values,
but sometimes also 32bit ones. Add helpers that allow for easy use of lwzx/stwx
in their respective byte-reverse or native form.

Signed-off-by: Alexander Graf <agraf@suse.de>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
KVM: PPC: Book3S HV: Make HTAB code LE host aware

When running on an LE host all data structures are kept in little endian
byte order. However, the HTAB still needs to be maintained in big endian.

So every time we access any HTAB we need to make sure we do so in the right
byte order. Fix up all accesses to manually byte swap.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S HV: Access guest VPA in BE

There are a few shared data structures between the host and the guest. Most
of them get registered through the VPA interface.

These data structures are defined to always be in big endian byte order, so
let's make sure we always access them in big endian.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S HV: Access host lppaca and shadow slb in BE

Some data structures are always stored in big endian. Among those are the LPPACA
fields as well as the shadow slb. These structures might be shared with a
hypervisor.

So whenever we access those fields, make sure we do so in big endian byte order.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S HV: Access XICS in BE

On the exit path from the guest we check what type of interrupt we received
if we received one. This means we're doing hardware access to the XICS interrupt
controller.

However, when running on a little endian system, this access is byte reversed.

So let's make sure to swizzle the bytes back again and virtually make XICS
accesses big endian.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S HV: Fix ABIv2 on LE

For code that doesn't live in modules we can just branch to the real function
names, giving us compatibility with ABIv1 and ABIv2.

Do this for the compiled-in code of HV KVM.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S HV: Enable for little endian hosts

Now that we've fixed all the issues that HV KVM code had on little endian
hosts, we can enable it in the kernel configuration for users to play with.

Signed-off-by: Alexander Graf <agraf@suse.de>