arm,kvm: update CP15 timer model when exiting Kvm

The ARM MiscRegs implementation has two interfaces: 'normal'
and 'no effect'. The latter acts as a way to access the
backing store without architectural 'effects'. For instance,
a normal write to a timer compare value would call into the
timer model to emulate the device. The 'no effect' interface,
however, would just write the value into the register backing
store and do nothing else.

For Kvm execution, a delicate balance must be struck for the
timer device specifically. We need the code in the model
to be run, because it contains state other than the register
backing store that must stay in sync. On the other hand, we
don't necessarily want the timer model to schedule gem5
events when this happens.

In this commit, we ensure that we use the 'effectful'
MiscReg interface when copying the CP15 timer registers
from Kvm back into gem5. The prior commit makes sure
that this doesn't generate unnecessary timer events
or interrupts.

Change-Id: Id414c2965bd07fc21ac95e3d581ccc9f55cef9f9
Reviewed-on: https://gem5-review.googlesource.com/3543
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

arm, kvm: Override the kernel's default MPIDR value

The kernel and gem5 derive MPIDR values from CPU IDs in slightly
different ways. This means that guests running in a multi-CPU setup
sometimes fail to bring up secondary CPUs. Fix this by overriding the
MPIDR value in virtual CPUs just after they have been instantiated.

Change-Id: I916d44978a9c855ab89c80a083af45b0cea6edac
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2461
Reviewed-by: Weiping Liao <weipingliao@google.com>

kvm, arm: Fix compilation errors due to API changes

The checkpoint changes, along with the SMT patches have changed a
number of APIs. Adapt the ArmKvmCPU accordingly.

misc: Remove redundant compiler-specific defines

This patch moves away from using M5_ATTR_OVERRIDE and the m5::hashmap
(and similar) abstractions, as these are no longer needed with gcc 4.7
and clang 3.1 as minimum compiler versions.

kvm, arm: Add support for aarch64

This changeset adds support for aarch64 in kvm. The CPU module
supports both checkpointing and online CPU model switching as long as
no devices are simulated by the host kernel. It currently has the
following limitations:

* The system register based generic timer can only be simulated by
the host kernel. Workaround: Use a memory mapped timer instead to
simulate the timer in gem5.

* Simulating devices (e.g., the generic timer) in the host kernel
requires that the host kernel also simulates the GIC.

* ID registers in the host and in gem5 must match for switching
between simulated CPUs and KVM. This is particularly important
for ID registers describing memory system capabilities (e.g.,
ASID size, physical address size).

* Switching between a virtualized CPU and a simulated CPU is
currently not supported if in-kernel device emulation is
used. This could be worked around by adding support for switching
to the gem5 (e.g., the KvmGic) side of the device models. A
simpler workaround is to avoid in-kernel device models
altogether.