cpu-kvm: Added informative error message

PerfKvmCounter::attach fails if the user doesn't have privileges to make
the perf_event_open syscall. This is the default privilege setting since
kernel 4.6. I've seen some users in the mailing list resort to running
as root; changing the perf_event_paranoid setting is an alternative.

Change-Id: I2bc6f76abb6e97bf34b408a611f64b1910f50a43
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17508
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

misc: Rename misc.(hh|cc) to logging.(hh|cc)

These files aren't a collection of miscellaneous stuff, they're the
definition of the Logger interface, and a few utility macros for
calling into that interface (panic, warn, etc.).

Change-Id: I84267ac3f45896a83c0ef027f8f19c5e9a5667d1
Reviewed-on: https://gem5-review.googlesource.com/6226
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>

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

style: fix missing spaces in control statements

Result of running 'hg m5style --skip-all --fix-control -a'.

kvm: Basic support for hardware virtualized CPUs

This changeset introduces the architecture independent parts required
to support KVM-accelerated CPUs. It introduces two new simulation
objects:

KvmVM -- The KVM VM is a component shared between all CPUs in a shared
memory domain. It is typically instantiated as a child of the
system object in the simulation hierarchy. It provides access
to KVM VM specific interfaces.

BaseKvmCPU -- Abstract base class for all KVM-based CPUs. Architecture
dependent CPU implementations inherit from this class
and implement the following methods:

* updateKvmState() -- Update the
architecture-dependent KVM state from the gem5
thread context associated with the CPU.

* updateThreadContext() -- Update the thread context
from the architecture-dependent KVM state.

* dump() -- Dump the KVM state using (optional).

In order to deliver interrupts to the guest, CPU
implementations typically override the tick() method and
check for, and deliver, interrupts prior to entering
KVM.

Hardware-virutalized CPU currently have the following limitations:
* SE mode is not supported.
* PC events are not supported.
* Timing statistics are currently very limited. The current approach
simply scales the host cycles with a user-configurable factor.
* The simulated system must not contain any caches.
* Since cycle counts are approximate, there is no way to request an
exact number of cycles (or instructions) to be executed by the CPU.
* Hardware virtualized CPUs and gem5 CPUs must not execute at the
same time in the same simulator instance.
* Only single-CPU systems can be simulated.
* Remote GDB connections to the guest system are not supported.

Additionally, m5ops requires an architecture specific interface and
might not be supported.