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This changeset adds support for synchronizing the FPU and SIMD state
of a virtual x86 CPU with gem5. It supports both the XSave API and the
KVM_(GET|SET)_FPU kernel API. The XSave interface can be disabled
using the useXSave parameter (in case of kernel
issues). Unfortunately, KVM_(GET|SET)_FPU interface seems to be buggy
in some kernels (specifically, the MXCSR register isn't always
synchronized), which means that it might not be possible to
synchronize MXCSR on old kernels without the XSave interface.
This changeset depends on the __float80 type in gcc and might not
build using llvm.
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There are cases when the segment registers in gem5 are not compatible
with VMX. This changeset works around all known such issues. Specifically:
* The accessed bits in CS, SS, DD, ES, FS, GS are forced to 1.
* The busy bit in TR is forced to 1.
* The protection level of SS is forced to the same protection level as
CS. The difference /seems/ to be caused by a bug in gem5's x86
implementation.
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This changeset adds support for KVM on x86. Full support is split
across a number of commits since some features are relatively
complex. This changeset includes support for:
* Integer state synchronization (including segment regs)
* CPUID (gem5's CPUID values are inserted into KVM)
* x86 legacy IO (remapped and handled by gem5's memory system)
* Memory mapped IO
* PCI
* MSRs
* State dumping
Most of the functionality is fairly straight forward. There are some
quirks to support PCI enumerations since this is done in the TLB(!) in
the simulated CPUs. We currently replicate some of that code.
Unlike the ARM implementation, the x86 implementation of the virtual
CPU does not use the cycles hardware counter. KVM on x86 simulates the
time stamp counter (TSC) in the kernel. If we just measure host cycles
using perfevent, we might end up measuring a slightly different number
of cycles. If we don't get the cycle accounting right, we might end up
rewinding the TSC, with all kinds of chaos as a result.
An additional feature of the KVM CPU on x86 is extended state
dumping. This enables Python scripts controlling the simulator to
request dumping of a subset of the processor state. The following
methods are currenlty supported:
* dumpFpuRegs
* dumpIntRegs
* dumpSpecRegs
* dumpDebugRegs
* dumpXCRs
* dumpXSave
* dumpVCpuEvents
* dumpMSRs
Known limitations:
* M5 ops are currently not supported.
* FPU synchronization is not supported (only affects CPU switching).
Both of the limitations will be addressed in separate commits.
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The KVM base class incorrectly assumed that handleIprRead and
handleIprWrite both return ticks. This is not the case, instead they
return cycles. This changeset converts the returned cycles to ticks
when handling IPR accesses.
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There is a possibility that the timespec used to arm a timer becomes
zero if the number of ticks used when arming a timer is close to the
resolution of the timer. Due to the semantics of POSIX timers, this
actually disarms the timer. This changeset fixes this issue by
eliminating the rounding error (we always round away from zero
now). It also reuses the minimum number of cycles, which were
previously only used for cycle-based timers, to calculate a more
useful resolution.
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Previously, the LSQ would instantiate MaxThreads LSQUnits in the body of it's
object, but it would only initialize numThreads LSQUnits as specified by the
user. This had the effect of leaving some LSQUnits uninitialized when the
number of threads was less than MaxThreads, and when adding statistics to the
LSQUnit that must be initialized, this caused the stats initialization check to
fail. By dynamically instantiating LSQUnits, they are all initialized and this
avoids uninitialized LSQUnits from floating around during runtime.
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This patch makes it possible to once again build gem5 without any
ISA. The main purpose is to enable work around the interconnect and
memory system without having to build any CPU models or device models.
The regress script is updated to include the NULL ISA target. Currently
no regressions make use of it, but all the testers could (and perhaps
should) transition to it.
--HG--
rename : build_opts/NOISA => build_opts/NULL
rename : src/arch/noisa/SConsopts => src/arch/null/SConsopts
rename : src/arch/noisa/cpu_dummy.hh => src/arch/null/cpu_dummy.hh
rename : src/cpu/intr_control.cc => src/cpu/intr_control_noisa.cc
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The branch predictor is guarded by having either the in-order or
out-of-order CPU as one of the available CPU models and therefore
should not be used in the BaseCPU. This patch moves the parameter to
the relevant CPU classes.
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This patch is a first step to getting NOISA working again. A number of
redundant includes make life more difficult than it has to be and this
patch simply removes them. There are also some redundant forward
declarations removed.
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This patch fixes up the comment formatting for isDrained in the timing
CPU.
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Added a couple missing updates to the notIdleFraction stat. Without
these, it sometimes gives a (not) idle fraction that is greater than 1
or less than 0.
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This patch addresses an issue with trace playback in the TrafficGen
where the trace was reset but the header was not read from the trace
when a captured trace was played back for a second time. This resulted
in parsing errors as the expected message was not found in the trace
file.
The header check is moved to an init funtion which is called by the
constructor and when the trace is reset. This ensures that the trace
header is read each time when the trace is replayed.
This patch also addresses a small formatting issue in a panic.
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This patch modifies the SimpleTimingCPU drain check to also consider
the fetch event. Previously, there was an assumption that there is
never a fetch event scheduled if the CPU is not executing
microcode. However, when a context is activated, a fetch even is
scheduled, and microPC() is zero.
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This patch fixes a bug in the O3 fetch stage that was introduced when
the cache line size was moved to the system. By mistake, the
initialisation and resetting of the fetch stage was merged and put in
the constructor. The resetting is now re-added where it should be.
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Remove unused virtual getBranchPred() method from BaseCPU as it is not
implemented by any of the CPU models. It used to always return NULL.
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This patch removes the notion of a peer block size and instead sets
the cache line size on the system level.
Previously the size was set per cache, and communicated through the
interconnect. There were plenty checks to ensure that everyone had the
same size specified, and these checks are now removed. Another benefit
that is not yet harnessed is that the cache line size is now known at
construction time, rather than after the port binding. Hence, the
block size can be locally stored and does not have to be queried every
time it is used.
A follow-on patch updates the configuration scripts accordingly.
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trace files for SE mode
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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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