arch: Include some additional headers in arch/generic/mmapped_ipr.cc.

These had been included transitively before.

Change-Id: Ie420bc957e9abb5cd01fcf720fc1fda619d210f0
Reviewed-on: https://gem5-review.googlesource.com/c/13538
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

arch: Explicitly specify the endianness in the generic mem helpers.

This avoids using the accessors which automatically assume an
endianness, requiring the memory system to know what the guest ISA is.

Change-Id: I863fa4116f00e77b801a2f8ea2fbe34e7f55fd5f
Reviewed-on: https://gem5-review.googlesource.com/c/13461
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

style: [patch 1/22] use /r/3648/ to reorganize includes

mem: Use a flag instead of address bit 63 for generic IPRs

Using address bit 63 to identify generic IPRs caused problems on
SPARC, where IPRs are heavily used. This changeset redefines how
generic IPRs are identified. Instead of using bit 63, we now use a
separate flag (GENERIC_IPR) a memory request.

arch: Add support for m5ops using mmapped IPRs

In order to support m5ops on virtualized CPUs, we need to either
intercept hypercall instructions or provide a memory mapped m5ops
interface. Since KVM does not normally pass the results of hypercalls
to userspace, which makes that method unfeasible. This changeset
introduces support for m5ops using memory mapped mmapped IPRs. This is
implemented by adding a class of "generic" IPRs which are handled by
architecture-independent code. Such IPRs always have bit 63 set and
are handled by handleGenericIprRead() and
handleGenericIprWrite(). Platform specific impementations of
handleIprRead and handleIprWrite should use
GenericISA::isGenericIprAccess to determine if an IPR address should
be handled by the generic code instead of the architecture-specific
code. Platforms that don't need their own IPR support can reuse
GenericISA::handleIprRead() and GenericISA::handleIprWrite().