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This patch adds the notion of source- and derived-clock domains to the
ClockedObjects. As such, all clock information is moved to the clock
domain, and the ClockedObjects are grouped into domains.
The clock domains are either source domains, with a specific clock
period, or derived domains that have a parent domain and a divider
(potentially chained). For piece of logic that runs at a derived clock
(a ratio of the clock its parent is running at) the necessary derived
clock domain is created from its corresponding parent clock
domain. For now, the derived clock domain only supports a divider,
thus ensuring a lower speed compared to its parent. Multiplier
functionality implies a PLL logic that has not been modelled yet
(create a separate clock instead).
The clock domains should be used as a mechanism to provide a
controllable clock source that affects clock for every clocked object
lying beneath it. The clock of the domain can (in a future patch) be
controlled by a handler responsible for dynamic frequency scaling of
the respective clock domains.
All the config scripts have been retro-fitted with clock domains. For
the System a default SrcClockDomain is created. For CPUs that run at a
different speed than the system, there is a seperate clock domain
created. This domain incorporates the CPU and the associated
caches. As before, Ruby runs under its own clock domain.
The clock period of all domains are pre-computed, such that no virtual
functions or multiplications are needed when calling
clockPeriod. Instead, the clock period is pre-computed when any
changes occur. For this to be possible, each clock domain tracks its
children.
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This patch removes the explicit setting of the clock period for
certain instances of CoherentBus, NonCoherentBus and IOCache where the
specified clock is same as the default value of the system clock. As
all the values used are the defaults, there are no performance
changes. There are similar cases where the toL2Bus is set to use the
parent CPU clock which is already the default behaviour.
The main motivation for these simplifications is to ease the
introduction of clock domains.
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This patch changes the IEW drain check to include the FU pool as there
can be instructions that are "stored" in FU completion events and thus
not covered by the existing checks. With this patch, we simply include
a check to see if all the FUs are considered non-busy in the next
tick.
Without this patch, the pc-switcheroo-full regression fails after
minor changes to the cache timing (aligning to clock edge).
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Reuse the address finalization code in the TLB instead of replicating
it when handling MMIO. This patch also adds support for injecting
memory mapped IPR requests into the memory system.
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This changeset adds the following stats to KVM:
* numVMHalfEntries: Number of entries into KVM to finalize pending
IO operations without executing guest instructions. These typically
happen as a result of a drain where the guest must finalize some
operations before the guest state is consistent.
* numExitSignal: Number of VM exits that have been triggered by a
signal. These usually happen as a result of the timer that limits
the time spent in KVM.
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We used to use the KVM CPU's clock to specify the host frequency. This
was not ideal for several reasons. One of them being that the clock
parameter of a CPU determines the frequency of some of the components
connected to the CPU. This changeset adds a separate hostFreq
parameter that should be used to specify the host frequency until we
add code to autodetect it. The hostFactor should still be used to
specify the conversion factor between the host performance and that of
the simulated system.
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We currently execute instructions in the guest and then handle any IO
request right after we break out of the virtualized environment. This
has the effect of executing IO requests in the exact same tick as the
first instruction in the sequence that was just run. There seem to be
cases where this simplification upsets some timing-sensitive devices.
This changeset splits execute and IO (and other services) across
multiple ticks. This is implemented by adding a separate
RunningService state to the CPU state machine. When a VM requires
service, it enters into this state and pending IO is then serviced in
the future instead of immediately. The delay between getting the
request and servicing it depends on the number of cycles executed in
the guest, which allows other components to catch up with the CPU.
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Update the system's totalNumInst counter when exiting from KVM and
maintain an internal absolute instruction count instead of relying on
the one from perf.
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Currently, the only way to get a CPU to stop after a fixed number of
instructions/loads is to set a property on the CPU that causes a
SimLoopExitEvent to be scheduled when the CPU is constructed. This is
clearly not ideal in cases where the simulation script wants the CPU
to stop at multiple instruction counts (e.g., SimPoint generation).
This changeset adds the methods scheduleInstStop() and
scheduleLoadStop() to the BaseCPU. These methods are exported to
Python and are designed to be used from the simulation script. By
using these methods instead of the old properties, a simulation script
can schedule a stop at any point during simulation or schedule
multiple stops. The number of instructions specified when scheduling a
stop is relative to the current point of execution.
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Some architectures have special registers in the guest that can be
used to do cycle accounting. This is generally preferrable since the
prevents the guest from seeing a non-monotonic clock. This changeset
adds a virtual method, getHostCycles(), that the architecture-specific
code can override to implement this functionallity. The default
implementation uses the hwCycles counter.
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timer_create can apparently return -1 and set errno to EAGAIN if the
kernel suffered a temporary failure when allocating a timer. This
happens from time to time, so we need to handle it.
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It is now required to initialize the thread context by calling
startup() on it. Failing to do so currently causes decoder in
x86-based CPUs to get very confused when restoring from checkpoints.
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This patch prunes the TraceCPU as the code is stale and the
functionality that it provided can now be achieved with the TrafficGen
using its trace playback mode.
The TraceCPU was able to play back pre-recorded memory traces of a few
different formats, and to achieve this level of flexibility with the
TrafficGen, use the util/encode_packet_trace (with suitable
modifications) to create a protobuf trace off-line.
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Add a check which ensures that the minumum period for the LINEAR and
RANDOM traffic generator states is less than or equal to the maximum
period. If the minimum period is greater than the maximum period a
fatal is triggered.
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This patch fixes a bug with the traffic generator which occured when
reading in the state transitions from the configuration
file. Previously, the size of the vector which stored the transitions
was used to get the size of the transitions matrix, rather than using
the number of states. Therefore, if there were more transitions than
states, i.e. some transitions has a probability of less than 1, then
the traffic generator would fatal when trying to check the
transitions.
This issue has been addressed by using the number of input states,
rather then the number of transitions.
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This patch adds an optional request elasticity to the traffic
generator, effectievly compensating for it in the case of the linear
and random generators, and adding it in the case of the trace
generator. The accounting is left with the top-level traffic
generator, and the individual generators do the necessary math as part
of determining the next packet tick.
Note that in the linear and random generators we have to compensate
for the blocked time to not be elastic, i.e. without this patch the
aforementioned generators will slow down in the case of back-pressure.
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This patch changes the queued port for a conventional master port and
stalls the traffic generator when requests are not immediately
accepted. This is a first step to allowing elasticity in the injection
of requests.
The patch also adds stats for the sent packets and retries, and
slightly changes how the nextPacketTick and getNextPacket
interact. The advancing of the trace is now moved to getNextPacket and
nextPacketTick is only responsible for answering the question when the
next packet should be sent.
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This patch moves the responsibility for sending packets out of the
generator states and leaves it with the top-level traffic
generator. The main aim of this patch is to enable a transition to
non-queued ports, i.e. with send/retry flow control, and to do so it
is much more convenient to not wrap the port interactions and instead
leave it all local to the traffic generator.
The generator states now only govern when they are ready to send
something new, and the generation of the packets to send. They thus
have no knowledge of the port that is used.
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This patch simplifies the object hierarchy of the traffic generator by
getting rid of the StateGraph class and folding this functionality
into the traffic generator itself.
The main goal of this patch is to facilitate upcoming changes by
reducing the number of affected layers.
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This patch changes the type of the hash function for BasicBlockRanges
to match the original definition of the templatized type. Without
this, clang raises a warning and combined with the "-Werror" flag this
causes compilation to fail.
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having separate params for the local/globalHistoryBits and the
local/globalPredictorSize can lead to inconsistencies if they
are not carefully set. this patch dervies the number of bits
necessary to index into the local/global predictors based on
their size.
the value of the localHistoryTableSize for the ARM O3 CPU has been
increased to 1024 from 64, which is more accurate for an A15 based
on some correlation against A15 hardware.
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Add the option useCoalescedMMIO to the BaseKvmCPU. The default
behavior is to disable coalesced MMIO since this hasn't been heavily
tested.
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The CpuPort class was removed before the KVM patches were committed,
which means that the KVM interface currently doesn't compile. This
changeset adds the BaseKvmCPU::KVMCpuPort class which derives from
MasterPort. This class is used on the data and instruction ports
instead of the old CpuPort.
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This changeset adds a 'numInsts' stat to the KVM-based CPU. It also
cleans up the variable names in kvmRun to make the distinction between
host cycles and estimated simulated cycles clearer. As a bonus
feature, it also fixes a warning (unreferenced variable) when
compiling in fast mode.
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Add a debug print (when the Checkpoint debug flag is set) on serialize
and unserialize. Additionally, dump the KVM state before
serializing. The KVM state isn't dumped after unserializing since the
state is loaded lazily on the next KVM entry.
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Device accesses are normally uncacheable. This change probably doesn't
make any difference since we normally disable caching when KVM is
active. However, there might be devices that check this, so we'd
better enable this flag to be safe.
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This patch ensures the flags are always initialised.
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This patch changes the TraceGen such that it uses the optional request
flags from the protobuf trace if they are present.
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This patch enables the use of the generator behaviours outside the
TrafficGen module. This is useful e.g. to allow packet replay modes
for other devices in the system without having to replace them with a
TrafficGen in the configuration files.
This change also enables more specific behaviours to be composed as
specific modules, e.g. BaseBandModem can use a number of generators
and have application-specific parameters based around a specific set
of generators.
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This changeset adds support for m5 pseudo-ops when running in
kvm-mode. Unfortunately, we can't trap the normal gem5 co-processor
entry in KVM (it doesn't seem to be possible to trap accesses to
non-existing co-processors). We therefore use BZJ instructions to
cause a trap from virtualized mode into gem5. The BZJ instruction is
becomes a normal branch to the gem5 fallback code when running in
simulated mode, which means that this patch does not need to change
the ARM ISA-specific code.
Note: This requires a patched host kernel.
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Architecture specific limitations:
* LPAE is currently not supported by gem5. We therefore panic if LPAE
is enabled when returning to gem5.
* The co-processor based interface to the architected timer is
unsupported. We can't support this due to limitations in the KVM
API on ARM.
* M5 ops are currently not supported. This requires either a kernel
hack or a memory mapped device that handles the guest<->m5
interface.
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Add support for using the CPU cycle counter instead of a normal POSIX
timer to generate timed exits to gem5. This should, in theory, provide
better resolution when requesting timer signals.
The perf-based timer requires a fairly recent kernel since it requires
a working PERF_EVENT_IOC_PERIOD ioctl. This ioctl has existed in the
kernel for a long time, but it used to be completely broken due to an
inverted match when the kernel copied things from user
space. Additionally, the ioctl does not change the sample period
correctly on all kernel versions which implement it. It is currently
only known to work reliably on kernel version 3.7 and above on ARM.
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Reduce the number of KVM->TC synchronizations by overloading the
getContext() method and only request an update when the TC is
requested as opposed to every time KVM returns to gem5.
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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.
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Add the options 'panic_on_panic' and 'panic_on_oops' to the
LinuxArmSystem SimObject. When these option are enabled, the simulator
panics when the guest kernel panics or oopses. Enable panic on panic
and panic on oops in ARM-based test cases.
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Previously, nextCycle() could return the *current* cycle if the current tick was
already aligned with the clock edge. This behavior is not only confusing (not
quite what the function name implies), but also caused problems in the
drainResume() function. When exiting/re-entering the sim loop (e.g., to take
checkpoints), the CPUs will drain and resume. Due to the previous behavior of
nextCycle(), the CPU tick events were being rescheduled in the same ticks that
were already processed before draining. This caused divergence from runs that
did not exit/re-entered the sim loop. (Initially a cycle difference, but a
significant impact later on.)
This patch separates out the two behaviors (nextCycle() and clockEdge()),
uses nextCycle() in drainResume, and uses clockEdge() everywhere else.
Nothing (other than name) should change except for the drainResume timing.
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This patch is based on http://reviews.m5sim.org/r/1474/ originally written by
Mitch Hayenga. Basic block vectors are generated (simpoint.bb.gz in simout
folder) based on start and end addresses of basic blocks.
Some comments to the original patch are addressed and hooks are added to create
and resume from checkpoints based on instruction counts dictated by external
SimPoint analysis tools.
SimPoint creation/resuming options will be implemented as a separate patch.
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This change fixes the switcheroo test that broke earlier this month. The code
that was checking for the pipeline being blocked wasn't checking for a pending
translation, only for a icache access.
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Currently the commit stage keeps a local copy of the interrupt object.
Since the interrupt is usually handled several cycles after the commit
stage becomes aware of it, it is possible that the local copy of the
interrupt object may not be the interrupt that is actually handled.
It is possible that another interrupt occurred in the
interval between interrupt detection and interrupt handling.
This patch creates a copy of the interrupt just before the interrupt
is handled. The local copy is ignored.
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This patch changes the port in the CPU classes to use MasterPort
instead of the derived CpuPort. The functions of the CpuPort are now
distributed across the relevant subclasses. The port accessor
functions (getInstPort and getDataPort) now return a MasterPort
instead of a CpuPort. This simplifies creating derivative CPUs that do
not use the CpuPort.
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This patch comments out the inclusion of the inorder TLBUnit which is
only used in the 9-stage pipeline. With the TLBUnit present, gcc >=
4.6 in combination with LTO ends up throwing away the definition of
the TLBUnit destructor, and consequently fail to link. See
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53808 for more details
about the bug, and http://gcc.gnu.org/ml/gcc/2012-06/msg00397.html for
the discussion thread that also touches on similar issues seen with
clang.
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The traffic generator used to incorrectly determine the next state in
when state 0 had a non-zero probability. Due to the way the next
transition was determined, state 0 could never be entered other than
as an initial state. This changeset updates the transitition() method
to correctly handle such cases and cases where the transition matrix
is a 1x1 matrix.
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This change fixes the switcheroo test that broke earlier this month. The code
that was checking for the pipeline being blocked wasn't checking for a pending
translation, only for a icache access.
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This patch fixes the warnings that clang3.2svn emit due to the "-Wall"
flag. There is one case of an uninitialised value in the ARM neon ISA
description, and then a whole range of unused private fields that are
pruned.
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This patch enables warnings for missing declarations. To avoid issues
with SWIG-generated code, the warning is only applied to non-SWIG
code.
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This patch address the most important name shadowing warnings (as
produced when using gcc/clang with -Wshadow). There are many
locations where constructor parameters and function parameters shadow
local variables, but these are left unchanged.
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This patch moves the 16x APIC clock divider to the Python code to
avoid the post-instantiation modifications to the clock. The x86 APIC
was the only object setting the clock after creation time and this
required some custom functionality and configuration. With this patch,
the clock multiplier is moved to the Python code and the objects are
instantiated with the appropriate clock.
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