dev-arm: rename Pl390 to GicV2

The Pl390 model has evolved and acquired a lot of the features from GICv2,
which means that the name is no longer appropriate. Rename it to GICv2
since this is more representative of the supported features.

GICv2 is backwards compatible with the older Pl390, so we decided to
simply rename the class to represent both GICv2 and older interfaces such
as the instead of creating a new separate one.

Change-Id: I1c05fba8b3cb5841c66480e9f05b8c873eba3229
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/12492
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

sim: Remove _numContexts member in System class

A System object has a _numContexts member variable which represent the
number of ThreadContext registered in the System. Since this has to
match the size of the ThreadContext vector, this patch removes the
manually cached size. This was usually used as a for-loop index, whereas
we want to enforce the use of range-based loops whenever possible.

Change-Id: I1ba317c0393bcc9c1aeebbb1fc22d7b2bc2cf90c
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8062
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>

kvm: arm: Get rid of functions which just wrap the subclasses version.

The MuxingKvmGic class defined a few functions related to checkpointing which
did nothing other than call the underlying Pl390 implementation. These are
unnecessary in general, and are particularly unnecessary for the loadState
function which is a very lightly used part of the checkpointing interface.
It's not actually defined in Pl390 either, and falls through to the
underlying implementation.

Change-Id: I84aae13d4966df0f4fdd1a72aee0bf1af01392ff
Reviewed-on: https://gem5-review.googlesource.com/4760
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

kvm, arm: don't create interrupt events while saving GIC state

If an interrupt was pending according to Kvm state during a drain,
the Pl390 model would create an interrupt event that could not be
serviced, preventing the system from draining. The proper behavior
is for the Pl390 not actively being used for simulation to just skip
the GIC state machine that delivers interrupts.

Change-Id: Icb37e7e992f1fb441a9b3a26daa1bb5a6fe19228
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3661
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

kvm, arm: Don't forward IRQ/FIQ when using the kernel's GIC

The BaseArmKvmCPU is responsible for forwarding the IRQ and FIQ
signals from gem5's simulated GIC to KVM. However, these signals
shouldn't be used when the in-kernel GIC emulator is used.

Instead of delivering the interrupts to the guest, we should just
ignore them since any such pending interrupts are likely to be an
artifact of CPU switching or incorrect draining.

Change-Id: I083b72639384272157f92f44a6606bdf0be7413c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sudhanshu Jha <sudhanshu.jha@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3660

kvm: move Kvm check from ARM Kvm GIC to System

The check was nearly completely generic anyway,
with the exception of the Kvm CPU type.

This will make it easier for other parts of the
codebase to do similar checks.

Change-Id: Ibfdd3d65e9e6cc3041b53b73adfabee1999283da
Reviewed-on: https://gem5-review.googlesource.com/3540
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

arm, kvm: implement GIC state transfer

This also allows checkpointing of a Kvm GIC via the Pl390 model.

Change-Id: Ic85d81cfefad630617491b732398f5e6a5f34c0b
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2444
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Weiping Liao <weipingliao@google.com>

arm, kvm: remove KvmGic

KvmGic functionality has been subsumed within the new MuxingKvmGic
model, which has Pl390 fallback when not using KVM for fast emulation.
This simplifies configuration and will enable checkpointing between
KVM emulation and full-system simulation.

Change-Id: Ie61251720064c512843015c075e4ac419a4081e8
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

arm, kvm: implement MuxingKvmGic

This device allows us to, when KVM support is detected and compiled in,
instantiate the same Gic device whether the actual simulation is with
KVM cores or simulated cores. Checkpointing is not yet supported.

Change-Id: I67e4e0b6fb7ab5058e52c933f4f3d8e7ab24981e
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

sim, kvm: make KvmVM a System parameter

A KVM VM is typically a child of the System object already, but for
solving future issues with configuration graph resolution, the most
logical way to keep track of this object is for it to be an actual
parameter of the System object.

Change-Id: I965ded22203ff8667db9ca02de0042ff1c772220
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

kvm, arm: Make GIC interrupt lines configurable

Add support for overriding the number of interrupt lines in the ARM
KvmGic.

Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Radhika Jagtap <radhika.jagtap@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

kvm, arm: Refactor KVM GIC device

Factor out the kernel device wrapper from the KvmGIC and put it in a
separate class. This will simplify a future kernel/gem5 hybrid GIC.

Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Radhika Jagtap <radhika.jagtap@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

sim: Refactor the serialization base class

Objects that are can be serialized are supposed to inherit from the
Serializable class. This class is meant to provide a unified API for
such objects. However, so far it has mainly been used by SimObjects
due to some fundamental design limitations. This changeset redesigns
to the serialization interface to make it more generic and hide the
underlying checkpoint storage. Specifically:

* Add a set of APIs to serialize into a subsection of the current
object. Previously, objects that needed this functionality would
use ad-hoc solutions using nameOut() and section name
generation. In the new world, an object that implements the
interface has the methods serializeSection() and
unserializeSection() that serialize into a named /subsection/ of
the current object. Calling serialize() serializes an object into
the current section.

* Move the name() method from Serializable to SimObject as it is no
longer needed for serialization. The fully qualified section name
is generated by the main serialization code on the fly as objects
serialize sub-objects.

* Add a scoped ScopedCheckpointSection helper class. Some objects
need to serialize data structures, that are not deriving from
Serializable, into subsections. Previously, this was done using
nameOut() and manual section name generation. To simplify this,
this changeset introduces a ScopedCheckpointSection() helper
class. When this class is instantiated, it adds a new /subsection/
and subsequent serialization calls during the lifetime of this
helper class happen inside this section (or a subsection in case
of nested sections).

* The serialize() call is now const which prevents accidental state
manipulation during serialization. Objects that rely on modifying
state can use the serializeOld() call instead. The default
implementation simply calls serialize(). Note: The old-style calls
need to be explicitly called using the
serializeOld()/serializeSectionOld() style APIs. These are used by
default when serializing SimObjects.

* Both the input and output checkpoints now use their own named
types. This hides underlying checkpoint implementation from
objects that need checkpointing and makes it easier to change the
underlying checkpoint storage code.

kvm, arm, dev: Add an in-kernel GIC implementation

This changeset adds a GIC implementation that uses the kernel's
built-in support for simulating the interrupt controller. Since there
is currently no support for state transfer between gem5 and the
kernel, the device model does not support serialization and CPU
switching (which would require switching to a gem5-simulated GIC).