mem: Minimize the use of MemObject.

MemObject doesn't provide anything beyond its base ClockedObject any
more, so this change removes it from most inheritance hierarchies.
Occasionally MemObject is replaced with SimObject when I was fairly
confident that the extra functionality of ClockedObject wasn't needed.

Change-Id: Ic014ab61e56402e62548e8c831eb16e26523fdce
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18289
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>

mem: Unify delayed packet deletion

This patch unifies how we deal with delayed packet deletion, where the
receiving slave is responsible for deleting the packet, but the
sending agent (e.g. a cache) is still relying on the pointer until the
call to sendTimingReq completes. Previously we used a mix of a
deletion vector and a construct using unique_ptr. With this patch we
ensure all slaves use the latter approach.

mem: Split port retry for all different packet classes

This patch fixes a long-standing isue with the port flow
control. Before this patch the retry mechanism was shared between all
different packet classes. As a result, a snoop response could get
stuck behind a request waiting for a retry, even if the send/recv
functions were split. This caused message-dependent deadlocks in
stress-test scenarios.

The patch splits the retry into one per packet (message) class. Thus,
sendTimingReq has a corresponding recvReqRetry, sendTimingResp has
recvRespRetry etc. Most of the changes to the code involve simply
clarifying what type of request a specific object was accepting.

The biggest change in functionality is in the cache downstream packet
queue, facing the memory. This queue was shared by requests and snoop
responses, and it is now split into two queues, each with their own
flow control, but the same physical MasterPort. These changes fixes
the previously seen deadlocks.

Port: Hide the queue implementation in SimpleTimingPort

This patch makes the queue implementation in the SimpleTimingPort
private to avoid confusion with the protected member queue in the
QueuedSlavePort. The SimpleTimingPort provides the queue_impl to the
QueuedSlavePort and it can be accessed via the reference in the base
class. The use of the member name queue is thus no longer overloaded.

mem: Delay deleting of incoming packets by one call.

This patch is a temporary fix until Andreas' four-phase patches
get reviewed and committed. Removing FastAlloc seems to have exposed
an issue which previously was reasonable rare in which packets are freed
before the sending cache is done with them. This change puts incoming packets
no a pendingDelete queue which are deleted at the start of the next call and
thus breaks the dependency between when the caller returns true and when the
packet is actually used by the sending cache.

Running valgrind on a multi-core linux boot and the memtester results in no
valgrind warnings.

MEM: Separate requests and responses for timing accesses

This patch moves send/recvTiming and send/recvTimingSnoop from the
Port base class to the MasterPort and SlavePort, and also splits them
into separate member functions for requests and responses:
send/recvTimingReq, send/recvTimingResp, and send/recvTimingSnoopReq,
send/recvTimingSnoopResp. A master port sends requests and receives
responses, and also receives snoop requests and sends snoop
responses. A slave port has the reciprocal behaviour as it receives
requests and sends responses, and sends snoop requests and receives
snoop responses.

For all MemObjects that have only master ports or slave ports (but not
both), e.g. a CPU, or a PIO device, this patch merely adds more
clarity to what kind of access is taking place. For example, a CPU
port used to call sendTiming, and will now call
sendTimingReq. Similarly, a response previously came back through
recvTiming, which is now recvTimingResp. For the modules that have
both master and slave ports, e.g. the bus, the behaviour was
previously relying on branches based on pkt->isRequest(), and this is
now replaced with a direct call to the apprioriate member function
depending on the type of access. Please note that send/recvRetry is
still shared by all the timing accessors and remains in the Port base
class for now (to maintain the current bus functionality and avoid
changing the statistics of all regressions).

The packet queue is split into a MasterPort and SlavePort version to
facilitate the use of the new timing accessors. All uses of the
PacketQueue are updated accordingly.

With this patch, the type of packet (request or response) is now well
defined for each type of access, and asserts on pkt->isRequest() and
pkt->isResponse() are now moved to the appropriate send member
functions. It is also worth noting that sendTimingSnoopReq no longer
returns a boolean, as the semantics do not alow snoop requests to be
rejected or stalled. All these assumptions are now excplicitly part of
the port interface itself.

MEM: Introduce the master/slave port sub-classes in C++

This patch introduces the notion of a master and slave port in the C++
code, thus bringing the previous classification from the Python
classes into the corresponding simulation objects and memory objects.

The patch enables us to classify behaviours into the two bins and add
assumptions and enfore compliance, also simplifying the two
interfaces. As a starting point, isSnooping is confined to a master
port, and getAddrRanges to slave ports. More of these specilisations
are to come in later patches.

The getPort function is not getMasterPort and getSlavePort, and
returns a port reference rather than a pointer as NULL would never be
a valid return value. The default implementation of these two
functions is placed in MemObject, and calls fatal.

The one drawback with this specific patch is that it requires some
code duplication, e.g. QueuedPort becomes QueuedMasterPort and
QueuedSlavePort, and BusPort becomes BusMasterPort and BusSlavePort
(avoiding multiple inheritance). With the later introduction of the
port interfaces, moving the functionality outside the port itself, a
lot of the duplicated code will disappear again.

MEM: Split SimpleTimingPort into PacketQueue and ports

This patch decouples the queueing and the port interactions to
simplify the introduction of the master and slave ports. By separating
the queueing functionality from the port itself, it becomes much
easier to distinguish between master and slave ports, and still retain
the queueing ability for both (without code duplication).

As part of the split into a PacketQueue and a port, there is now also
a hierarchy of two port classes, QueuedPort and SimpleTimingPort. The
QueuedPort is useful for ports that want to leave the packet
transmission of outgoing packets to the queue and is used by both
master and slave ports. The SimpleTimingPort inherits from the
QueuedPort and adds the implemention of recvTiming and recvFunctional
through recvAtomic.

The PioPort and MessagePort are cleaned up as part of the changes.

MEM: Simplify cache ports preparing for master/slave split

This patch splits the two cache ports into a master (memory-side) and
slave (cpu-side) subclass of port with slightly different
functionality. For example, it is only the CPU-side port that blocks
incoming requests, and only the memory-side port that schedules send
events outside of what the transmit list dictates.

This patch simplifies the two classes by relying further on
SimpleTimingPort and also generalises the latter to better accommodate
the changes (introducing trySendTiming and scheduleSend). The
memory-side cache port overrides sendDeferredPacket to be able to not
only send responses from the transmit list, but also send requests
based on the MSHRs.

A follow on patch further simplifies the SimpleTimingPort and the
cache ports.

MEM: Separate queries for snooping and address ranges

This patch simplifies the address-range determination mechanism and
also unifies the naming across ports and devices. It further splits
the queries for determining if a port is snooping and what address
ranges it responds to (aiming towards a separation of
cache-maintenance ports and pure memory-mapped ports). Default
behaviours are such that most ports do not have to define isSnooping,
and master ports need not implement getAddrRanges.

MEM: Simplify ports by removing EventManager

This patch removes the inheritance of EventManager from the ports and
moves all responsibility for event queues to the owner. Eventually the
event manager should be the interface block, which could either be the
structural owner or a subblock like a LSQ in the O3 CPU for example.

includes: sort all includes

Replace curTick global variable with accessor functions.
This step makes it easy to replace the accessor functions
(which still access a global variable) with ones that access
per-thread curTick values.

Clean up the SimpleTimingPort class a little bit.
Move the constructor into the .cc file and get rid of the typedef for
SendEvent.

eventq: convert all usage of events to use the new API.
For now, there is still a single global event queue, but this is
necessary for making the steps towards a parallelized m5.

memory system: fix functional access bug.
Make sure not to keep processing functional accesses
after they've been responded to.
Also use checkFunctional() return value instead of checking
packet command field where possible, mostly just for consistency.

Fix up a few statistics problems.
Stats pretty much line up with old code, except:
- bug in old code included L1 latency in L2 miss time, making it too high
- UniCoherence did cache-to-cache transfers even from non-owner caches,
so occasionally the icache would get a block from the dcache not the L2
- L2 can now receive ReadExReq from L1 since L1s have coherence

Get rid of requestCauses. Use timestamped queue to make
sure we don't re-request bus prematurely. Use callback to
avoid calling sendRetry() recursively within recvTiming.

A little more cleanup & refactoring of SimpleTimingPort.
Make it a better base class for cache ports.

Restructure SimpleTimingPort a bit:
- factor out checkFunctional() code so it can be
called from derived classes
- use EventWrapper for sendEvent, move event handling
code from event to port where it belongs
- make sendEvent a pointer so derived classes can
override it
- replace std::pair with new class for readability

Merge ktlim@zizzer:/bk/newmem
into zamp.eecs.umich.edu:/z/ktlim2/clean/newmem-busfix

configs/example/fs.py:
configs/example/se.py:
src/mem/tport.hh:
Hand merge.

Fix simple timing port keep a list of all packets, have only one event, and scan all packets on a functional access.

Ports now have a pointer to the MemObject that owns it (can be NULL).

src/cpu/simple/atomic.hh:
Port now takes in the MemObject that owns it.
src/cpu/simple/timing.hh:
Port now takes in MemObject that owns it.
src/dev/io_device.cc:
src/mem/bus.hh:
Ports now take in the MemObject that owns it.
src/mem/cache/base_cache.cc:
Ports now take in the MemObject that own it.
src/mem/port.hh:
src/mem/tport.hh:
Ports now optionally take in the MemObject that owns it.

Use PacketPtr everywhere

Move more common functionality into SimpleTimingPort,
allowing derived classes to be simplified.

Minor include file & formatting cleanup.

Move PioPort timing code into Simple Timing Port object
Make PioPort use it
Make Physical memory use it as well

src/SConscript:
Add timing port to sconscript
src/dev/io_device.cc:
src/dev/io_device.hh:
Move simple timing pio port stuff into a simple timing port class so it can be used by the physical memory
src/mem/physical.cc:
src/mem/physical.hh:
use a simple timing port stuff instead of rolling our own here