It's apparently not widely known that our scons scripts allow you to
put the build directory wherever you want; not only does it not have
to be immediately under the root of your repo, it doesn't even have
to be underneath the root at all. (For example, sometimes it's useful
to build on a local disk if your repo is on a slow NFS mount.)
I point this out because this functionality has been broken for close
to two years but no one seems to have noticed yet. This patch fixes
an assumption that crept in in changeset be0e1724eb39 (May 09 2014)
that the build dir would be immediately under the top level of the
repo, preventing builds anywhere else.
Adding voltage function which returns the current voltage
for a given clocked object. It's handy for power models and
similar stuff that need to retrieve voltage. Function
frequency() is already there, so I see no reason for not having
this one too.
fu_pool and inst_queue were using -1 for "no such FU" and -2 for "all those
FUs are busy at the moment" when requesting for a FU and replying. This
patch introduces new constants NoCapableFU and NoFreeFU respectively.
In addition, the condition (idx == -2 || idx != -1) is equivalent to
(idx != -1), so this patch also simplifies that.
--HG--
extra : rebase_source : 4833717b9d1e09d7594d1f34f882e13fc4b86846
We can't/shouldn't use KVM after a fork since the child and parent
probably point to the same VM. Knowing the exact effects of this is
hard, but they are likely to be messy. We also disconnect the
performance counters attached to the guest. This works around what
seems to be a kernel bug where spurious SIGIOs get delivered to the
forked child process.
Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
[andreas.sandberg@arm.com: Fatal if entering KVM in child process ]
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
This changeset adds forking capabilities to the gem5 python scripts. A fork
method is added to simulate.py. This method is responsible for forking the
simulator itself, and will direct all output files to a new output directory
based on the fork sequence number. The default name of the output directory is
the same as the parent with the suffix ".fN" added where N is the fork sequence
number. The fork method provides the option to specify if the system should be
drained prior to forking, or not. By default the system is drained to ensure
that there are no in-flight transactions.
When forking the simulator, the fork method returns the PID of the child
process, or returns 0 if running in the child. This is in line with the standard
Python forking interface.
Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
[andreas.sandberg@arm.com: Updated to comply with modern draining semantics ]
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
This changeset adds support for notifying the disk images that the simulator has
been forked. We need to disable the saving of the CoW disk image from the child
process, and we need to make sure that systems which use a raw disk image are
not allowed to fork to avoid two or more gem5 processes writing to the same disk
image.
Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
When forking a gem5 process, some objects need to clean up resources
(mainly file descriptions) shared between the child and the parent of
the fork. This changeset adds the notifyFork() method to Drainable,
which is called in the child process.
Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
This changeset adds support for changing the simulator output
directory. This can be useful when the simulation goes through several
stages (e.g., a warming phase, a simulation phase, and a verification
phase) since it allows the output from each stage to be located in a
different directory. Relocation is done by calling core.setOutputDir()
from Python or simout.setOutputDirectory() from C++.
This change affects several parts of the design of the gem5's output
subsystem. First, files returned by an OutputDirectory instance (e.g.,
simout) are of the type OutputStream instead of a std::ostream. This
allows us to do some more book keeping and control re-opening of files
when the output directory is changed. Second, new subdirectories are
OutputDirectory instances, which should be used to create files in
that sub-directory.
Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
This patch adds assertions that enforce that only invalidating snoops
will ever reach into the logic that tracks in-order load completion and
also invalidation of LL/SC (and MONITOR / MWAIT) monitors. Also adds
some comments to MSHR::replaceUpgrades().
Writes to locked memory addresses (LLSC) did not wake up the locking
CPU. This can lead to deadlocks on multi-core runs. In AtomicSimpleCPU,
recvAtomicSnoop was checking if the incoming packet was an invalidation
(isInvalidate) and only then handled a locked snoop. But, writes are
seen instead of invalidates when running without caches (fast-forward
configurations). As as simple fix, now handleLockedSnoop is also called
even if the incoming snoop packet are from writes.
Properly done for the ERET instruction in v8, but not for v7.
Many control register changes are only visible after explicit
instruction synchronization barriers or exception entry/exit.
This means mode changing instructions should squash any
younger in-flight speculative instructions.
This patch fixes an issue where an InvalidationReq only traversed one
level of the cache hierarchy, and was subsequently turned into a
ReadExReq due to it needing writable, and the command not being
checked for explicitly.
Bug fix for check on protobuf file frequency being different than
global frequency.
The ASCII encoder script is also fixed, and the example trace used in
the regressions is updated.
Add a callback handler for the NoMali reset callback. This callback is
called whenever the GPU is reset using the register interface or the
NoMali API. The callback can be used to override ID registers using
the raw register API.
Refactor and cleanup the NoMaliGpu class:
* Use a std::map instead of a switch block to map the parameter enum
describing the GPU type to a NoMali type.
* Remove redundant NoMali handle from the interrupt callback.
* Make callbacks and API wrappers protected instead of private to
enable future extensions.
* Wrap remaining NoMali API calls.
Both Memory Fence is now flagged as Global Memory only to avoid resource
oversubscribing.
Flat instructions now check for Shared Memory resource busy to avoid
oversubscribing resources.
All WaitClass resources now use cycles (not ticks) to register the number
of pipe stages between Scoreboard and Execute to be consistent with
instruction scheduling logic which always used clock cycles.
This patch essentially rolls back 10518:30e3715c9405 to make RubyPort the
parent class of DMASequencer. It removes redundant code and restores some
features which were lost when directly inheriting from MemObject. For
example,
DMASequencer can now communicate to other devices using PIO, which is useful
for memmory-mapped communication between multiple DMADevices.
This patch adds a --debug-end flag to main.py so that debug output can be
stoped at a specified tick, while allowing the simulation to continue. It is
useful in situations where you would like to produce a trace for a region of
interest while still collecting stats for the entire run. This is in contrast
to the currently existing --debug-break flag, which terminates the simulation
at the tick.
Avoid being overly conservative in clearing load locks in the cache,
and allow writes to the line if they are from the same context. This
is in line with ALPHA and ARM.
This patch introduces the ability of making the coherent crossbar the
point of coherency. If so, the crossbar does not forward packets where
a cache with ownership has already committed to responding, and also
does not forward any coherency-related packets that are not intended
for a downstream memory controller. Thus, invalidations and upgrades
are turned around in the crossbar, and the memory controller only sees
normal reads and writes.
In addition this patch moves the express snoop promotion of a packet
to the crossbar, thus allowing the downstream cache to check the
express snoop flag (as it should) for bypassing any blocking, rather
than relying on whether a cache is responding or not.
Adopt the same flow as in timing mode, where the caches on the path to
memory get to keep the line (if present), and we use the
responderHadWritable flag to determine if we need to forward the
(invalidating) packet or not.
This patch unifies the snoop handling in case of hitting writebacks
with how we handle snoops hitting in the tags. As a result, we end up
using the same optimisation as the normal snoops, where we inform the
downstream cache if we encounter a line in Modified (writable and
dirty) state, which enables us to avoid sending out express snoops to
invalidate any Shared copies of the line. A few regressions
consequently change, as some transactions are sunk higher up in the
cache hierarchy.
This patch changes how the cache determines if snoops should be
forwarded from the memory side to the CPU side. Instead of having a
parameter, the cache now looks at the port connected on the CPU side,
and if it is a snooping port, then snoops are forwarded. Less error
prone, and less parameters to worry about.
The patch also tidies up the CPU classes to ensure that their I-side
port is not snooping by removing overrides to the snoop request
handler, such that snoop requests will panic via the default
MasterPort implement
Due to insufficient build deps, the checkpoint tags might not get
updated; this commit solves this. Due to the uncommon nature of the
build target, regenerating tags.cc is a fairly clean solution. Since
SCons hashes file contents, it won't recompile anything unless a new
checkpoint upgrader is actually added.
--HG--
extra : amend_source : ed3879da7668554693f697076deaf5029cc9b954
The previous implementation did a pair of nested RMW operations,
which isn't compatible with the way that locked RMW operations are
implemented in the cache models. It was convenient though in that
it didn't require any new micro-ops, and supported cmpxchg16b using
64-bit memory ops. It also worked in AtomicSimpleCPU where
atomicity was guaranteed by the core and not by the memory system.
It did not work with timing CPU models though.
This new implementation defines new 'split' load and store micro-ops
which allow a single memory operation to use a pair of registers as
the source or destination, then uses a single ldsplit/stsplit RMW
pair to implement cmpxchg. This patch requires support for 128-bit
memory accesses in the ISA (added via a separate patch) to support
cmpxchg16b.
Although the cache models support wider accesses, the ISA descriptions
assume that (for the most part) memory operands are integer types,
which makes it difficult to define instructions that do memory accesses
larger than 64 bits.
This patch adds some generic support for memory operands that are arrays
of uint64_t, and specifically a 'u2qw' operand type for x86 that is an
array of 2 uint64_ts (128 bits). This support is unused at this point,
but will be needed shortly for cmpxchg16b. Ideally the 128-bit SSE
memory accesses will also be rewritten to use this support.
Support for 128-bit accesses could also have been added using the gcc
__int128_t extension, which would have been less disruptive. However,
although clang also supports __int128_t, it's still non-standard.
Also, more importantly, this approach creates a path to defining
256- and 512-byte operands as well, which will be useful for eventual
AVX support.
MemOperand variables were being initialized to 0
"to avoid 'uninitialized variable' errors" but these
no longer seem to be a problem (with the exception of
one use case in POWER that is arguably broken and
easily fixed here).
Getting rid of the initialization is necessary to
set up a subsequent patch which extends memory
operands to possibly not be scalars, making the
'= 0' initialization no longer feasible.
Writing 16 bytes from an 8-byte source value is a bad idea.
This doesn't appear to have broken anything, but showed up
as spurious differences when tracediffing runs.
Result of running 'hg m5style --skip-all --fix-control -a' to get
rid of '== true' comparisons, plus trivial manual edits to get
rid of '== false'/'== False' comparisons.
Left a couple of explicit comparisons in where they didn't seem
unreasonable:
invalid boolean comparison in src/arch/mips/interrupts.cc:155
>> DPRINTF(Interrupt, "Interrupts OnCpuTimerINterrupt(tc) == true\n");<<
invalid boolean comparison in src/unittest/unittest.hh:110
>> "EXPECT_FALSE(" #expr ")", (expr) == false)<<
In the process of trying to get rid of an '== false' comparison,
it became apparent that a slightly more involved solution was
needed. Split this out into its own changeset since it's not
a totally trivial local change like the others.
mem: support for gpu-style RMWs in ruby
This patch adds support for GPU-style read-modify-write (RMW) operations in
ruby. Such atomic operations are traditionally executed at the memory controller
(instead of through an L1 cache using cache-line locking).
Currently, this patch works by propogating operation functors through the memory
system.
Just changes the metavar for --debug-start from TIME
to TICK in cset 72046b9b3323 and didn't notice that the
comment "must be in ticks" is now redundant.
For historical reasons, the ExecContext interface had a single
function, readMem(), that did two different things depending on
whether the ExecContext supported atomic memory mode (i.e.,
AtomicSimpleCPU) or timing memory mode (all the other models).
In the former case, it actually performed a memory read; in the
latter case, it merely initiated a read access, and the read
completion did not happen until later when a response packet
arrived from the memory system.
This led to some confusing things, including timing accesses
being required to provide a pointer for the return data even
though that pointer was only used in atomic mode.
This patch splits this interface, adding a new initiateMemRead()
function to the ExecContext interface to replace the timing-mode
use of readMem().
For consistency and clarity, the readMemTiming() helper function
in the ISA definitions is renamed to initiateMemRead() as well.
For x86, where the access size is passed in explicitly, we can
also get rid of the data parameter at this level. For other ISAs,
where the access size is determined from the type of the data
parameter, we have to keep the parameter for that purpose.
The read() function merely initiates a memory read operation; the
data doesn't arrive until the access completes and a response packet
is received from the memory system. Thus there's no need to provide
a data pointer; its existence is historical.
Getting this pointer out of this internal o3 interface sets the
stage for similar cleanup in the ExecContext interface. Also
found that we were pointlessly setting the contents at this pointer
on a store forward (the useful memcpy happens just a few lines
below the deleted one).
The readMemAtomic/writeMemAtomic helper functions were calling
readMemTiming/writeMemTiming respectively. This is functionally
correct, since the *Timing functions are doing the same access
initiation operation as the *Atomic functions (just that the
*Atomic versions also complete the access in line). It also
provides for some (very minimal) code reuse. Unfortunately,
it's potentially pretty confusing, since it makes it look like
the atomic accesses are somehow being converted to timing
accesses. It also gets in the way of specializing the timing
interface (as will be done in a future patch).
By ignoring SIG_TRAP, using --debug-break <N> when not connected to
a debugger becomes a no-op. Apparently this was intended to be a
feature, though the rationale is not clear.
If we don't ignore SIG_TRAP, then using --debug-break <N> when not
connected to a debugger causes the simulation process to terminate
at tick N. This is occasionally useful, e.g., if you just want to
collect a trace for a specific window of execution then you can combine
this with --debug-start to do exactly that.
In addition to not ignoring the signal, this patch also updates
the --debug-break help message and deletes a handful of unprotected
calls to Debug::breakpoint() that relied on the prior behavior.
Add a platform with support for both aarch32 and aarch64. This
platform implements a subset of the devices in a real Versatile
Express and extends it with some gem5-specific functionality. It is in
many ways similar to the old VExpress_EMM64 platform, but supports the
following new features:
* Automatic PCI interrupt assignment
* PCI interrupts allocated in a contiguous range.
* Automatic boot loader selection (32-bit / 64-bit)
* Cleaner memory map where gem5-specific devices live in CS5 which
isn't used by current Versatile Express platforms.
* No fake devices. Devices that were previously faked will be
removed from the device tree instead.
* Support for 510 GiB contiguous memory
Add support for automatic PCI interrupt routing using a device's ID on
the PCI bus. Our current DTBs typically tell the kernel that we do
this or something similar when declaring the PCI controller. This
changeset adds an option to make the simulator behave in the same way.
Interrupt routing can be selected by setting the int_policy parameter
in the GenericArmPciHost. The following values are supported:
* ARM_PCI_INT_STATIC: Use the old static routing policy using the
interrupt line from a device's configurtion space.
* ARM_PCI_INT_DEV: Use device number on the PCI bus to map to an
interrupt in the GIC. The interrupt is computed as:
gic_int = int_base + (pci_dev % int_count)
* ARM_PCI_INT_PIN: Use device interrupt pin on the PCI bus to map to
an interrupt in the GIC. The PCI specification reserves pin ID 0
for devices without interrupts, the interrupt therefore computed
as:
gic_int = int_base + ((pin - 1) % int_count)
The new Packet::setRaw() method incorrectly still contained
an htog() conversion. As a result, calls to the old set()
method (now defined as setRaw(htog(v))) underwent two htog
conversions, which breaks things when htog() is not a no-op.
Interestingly the only test that caught this was a SPARC
boot test, where an IsaFake device with a non-zero return
value was getting swapped twice resulting in a register
getting loaded with 0x100000000000000 instead of 1.
(Good reason for keeping SPARC around, perhaps?)
This patch replaces the gzstream zlib wrapper with the iostream3
wrapper provided as part of zlib contributions. The main reason for
the switch is to avoid including LGPL in the default gem5
build. iostream3 is provided under a more permissive license:
The code is provided "as is", with the permission to use, copy,
modify, distribute and sell it for any purpose without fee.
Distributed gem5 (abbreviated dist-gem5) is the result of the
convergence effort between multi-gem5 and pd-gem5 (from Univ. of
Wisconsin). It relies on the base multi-gem5 infrastructure for packet
forwarding, synchronisation and checkpointing but combines those with
the elaborated network switch model from pd-gem5.
--HG--
rename : src/dev/net/multi_etherlink.cc => src/dev/net/dist_etherlink.cc
rename : src/dev/net/multi_etherlink.hh => src/dev/net/dist_etherlink.hh
rename : src/dev/net/multi_iface.cc => src/dev/net/dist_iface.cc
rename : src/dev/net/multi_iface.hh => src/dev/net/dist_iface.hh
rename : src/dev/net/multi_packet.hh => src/dev/net/dist_packet.hh
Some of the DPRINTFs added to the classic cache in cset 45df88079f04,
while useful to those unfamiliar with the cache code, end up being
noise when you're familiar with the code but are trying to debug tricky
protocol issues. (Particularly getting two messages from each cache
as it receives a snoop request then declares that there was no match.)
This patch introduces a CacheVerbose debug flag, and moves a subset of
the added DPRINTFs into that category, so that Cache by itself returns
to being a more succinct summary of cache activity.
Also added a CacheAll compound flag to turn on all the cache-related
debug flags (other than CacheTags, which you *really* have to want badly
to turn it on, IMO).
This patch removes the NeedsWritable flag for all responses, as it is
really only the request that needs a writable response. The response,
on the other hand, should in these cases always provide the line in a
writable state, as indicated by the hasSharers flag not being set.
When we send requests that has NeedsWritable set, the response will
always have the hasSharers flag not set. Additionally, there are cases
where the request did not have NeedsWritable set, and we still get a
writable response with the hasSharers flag not set. This never happens
on snoops, but is used by downstream caches to pass ownership
upstream.
As part of this patch, the affected response types are updated, and
the snoop filter is similarly modified to check only the hasSharers
flag (as it should). A sanity check is also added to the packet class,
asserting that we never look at the NeedsWritable flag for responses.
No regressions are affected.
This patch looks at the request and response command to determine if
either actually has any data payload, and if not, we do not allocate
any space for packet data.
The only tricky case is where the command type is changed as part of
the MSHR functionality. In these cases where the original packet had
no data, but the new packet does, we need to explicitly call
allocate().
This patch ensures we do not respond with a Modified (dirty and
writable) line if the request is uncacheable, and that the cache
responding retains the line without modifying the state (even if
responding).
This patch changes the name of a bunch of packet flags and MSHR member
functions and variables to make the coherency protocol easier to
understand. In addition the patch adds and updates lots of
descriptions, explicitly spelling out assumptions.
The following name changes are made:
* the packet memInhibit flag is renamed to cacheResponding
* the packet sharedAsserted flag is renamed to hasSharers
* the packet NeedsExclusive attribute is renamed to NeedsWritable
* the packet isSupplyExclusive is renamed responderHadWritable
* the MSHR pendingDirty is renamed to pendingModified
The cache states, Modified, Owned, Exclusive, Shared are also called
out in the cache and MSHR code to make it easier to understand.
This patch is imported from reviewboard patch 2551 by Nilay.
This patch moves from a dynamically defined MachineType to a statically
defined one. The need for this patch was felt since a dynamically defined
type prevents us from having types for which no machine definition may
exist.
The following changes have been made:
i. each machine definition now uses a type from the MachineType enumeration
instead of any random identifier. This required changing the grammar and the
*.sm files.
ii. MachineType enumeration defined statically in RubySlicc_Exports.sm.
* * *
normal protocol fixes for nilay's parser machine type fix
This patch is imported from reviewboard patch 2550 by Nilay.
It was possible to specify multiple machine types with a single state machine.
This seems unnecessary and is being removed.
Add a sanity check to make it explicit that we currently do not allow
an I/O coherent agent to directly issue writes into the coherent part
of the memory system (it has to go via a cache, and get transformed
into a read ex, upgrade or invalidation).
This patch changes how the cache tracks which snoops are forwarded,
and which ones are created locally. Previously the identification was
based on an empty sender state of a specific class, but this method
fails to distinguish which cache actually attached the sender
state. Instead we use the same mechanism as the crossbar, and keep
track of the requests that have outstanding snoops.
This patch addresses a bug in how the cache attached the MSHR as a
sender state. Rather than overwriting any existing sender state it now
pushes a new one. The handling of upward snoops is also clarified.
Currently, the wire format of register values in g- and G-packets is
modelled using a union of uint8/16/32/64 arrays. The offset positions
of each register are expressed as a "register count" scaled according
to the width of the register in question. This results in counter-
intuitive and error-prone "register count arithmetic", and some
formats would even be altogether unrepresentable in such model, e.g.
a 64-bit register following a 32-bit one would have a fractional index
in the regs64 array.
Another difficulty is that the array is allocated before the actual
architecture of the workload is known (and therefore before the correct
size for the array can be calculated).
With this patch I propose a simpler mechanism for expressing the
register set structure. In the new code, GdbRegCache is an abstract
class; its subclasses contain straightforward structs reflecting the
register representation. The determination whether to use e.g. the
AArch32 vs. AArch64 register set (or SPARCv8 vs SPARCv9, etc.) is made
by polymorphically dispatching getregs() to the concrete subclass.
The subclass is not instantiated until it is needed for actual
g-/G-packet processing, when the mode is already known.
This patch is not meant to be merged in on its own, because it changes
the contract between src/base/remote_gdb.* and src/arch/*/remote_gdb.*,
so as it stands right now, it would break the other architectures.
In this patch only the base and the ARM code are provided for review;
once we agree on the structure, I will provide src/arch/*/remote_gdb.*
for the other architectures; those patches could then be merged in
together.
Review Request: http://reviews.gem5.org/r/3207/
Pushed by Joel Hestness <jthestness@gmail.com>
When adding an option to forward work items to the Python environment,
the new behavior was accidentally enabled by default. Set the value of
exit_on_work_items to False by default to revert to the old behavior
unless the simulation scripts explicitly requests work item
forwarding.
This patch fixes a corner case in the deferred snoop handling, where
requests ended up being used by multiple packets with different
lifetimes, and inadvertently got deleted while they were still in use.
There are cases where we want the Python world to handle work items
instead of the C++ world. However, that's currently not possible. This
changeset adds the forward_work_items option to the System class. Then
it is set to True, work items will generate workbegin/workend
simulation exists with the work item ID as the exit code and the old
C++ handling is completely bypassed.
--HG--
extra : rebase_source : 8de637a744fc4b6ff2bc763f00cdf8ddf2bff885
This patch allows the ruby random tester to use ruby ports that may only
support instr or data requests. This patch is similar to a previous changeset
(8932:1b2c17565ac8) that was unfortunately broken by subsequent changesets.
This current patch implements the support in a more straight-forward way.
Since retries are now tested when running the ruby random tester, this patch
splits up the retry and drain check behavior so that RubyPort children, such
as the GPUCoalescer, can perform those operations correctly without having to
duplicate code. Finally, the patch also includes better DPRINTFs for
debugging the tester.
Move pcidev.(hh|cc) to src/dev/pci/device.(hh|cc) and update existing
devices to use the new header location. This also renames the PCIDEV
debug flag to have a capitalization that is consistent with the PCI
host and other devices.
--HG--
rename : src/dev/Pci.py => src/dev/pci/PciDevice.py
rename : src/dev/pcidev.cc => src/dev/pci/device.cc
rename : src/dev/pcidev.hh => src/dev/pci/device.hh
rename : src/dev/pcireg.h => src/dev/pci/pcireg.h
The writefile pseudo instruction uses OutputDirectory::create and
OutputDirectory::openFile to create the output files. However, by
default these will check the file extention for .gz, and create a gzip
compressed stream if the file ending matches. When writing out files,
we want to write them out exactly as they are in the guest simulation,
and never want to compress them with gzio. Additionally, this causes
m5 writefile to fail when checking the error flags for the output
steam.
With this patch we add an additional no_gz argument to
OutputDirectory::create and OutputDirectory::openFile which allows us
to override the gzip compression. Therefore, for m5 writefile we
disable the filename check, and always create a standard ostream.
Previous ARM-based simulations were limited to 8 cores due to
limitations in GICv2 and earlier. This changeset adds a set of
gem5-specific extensions that enable support for up to 256 cores.
When the gem5 extensions are enabled, the GIC uses CPU IDs instead of
a CPU bitmask in the GIC's register interface. To OS can enable the
extensions by setting bit 0x200 in ICDICTR.
This changeset is based on previous work by Matt Evans.
There's a well-meaning check in Process::allocFD() to return an invalid
target fd (-1) if the incoming host fd is -1. However, this means that
emulated drivers, which want to allocate a target fd that doesn't
correspond to a host fd, can't use -1 to indicate an intentionally
invalid host fd.
It turns out the allocFD() check is redundant, as callers always test
the host fd for validity before calling. Also, callers never test the
return value of allocFD() for validity, so even if the test failed,
it would likely have the undesirable result of returning -1 to the
target app as a file descriptor without setting errno.
Thus the check is pointless and is now getting in the way, so it seems
we should just get rid of it.
This patch adds support to optionally capture the virtual address and asid
for load/store instructions in the elastic traces. If they are present in
the traces, Trace CPU will set those fields of the request during replay.
This patch replaces the booleans that specified the elastic trace record
type with an enum type. The source of change is the proto message for
elastic trace where the enum is introduced. The struct definitions in the
elastic trace probe listener as well as the Trace CPU replace the boleans
with the proto message enum.
The patch does not impact functionality, but traces are not compatible with
previous version. This is preparation for adding new types of records in
subsequent patches.
This patch defines a TraceCPU that replays trace generated using the elastic
trace probe attached to the O3 CPU model. The elastic trace is an execution
trace with data dependencies and ordering dependencies annoted to it. It also
replays fixed timestamp instruction fetch trace that is also generated by the
elastic trace probe.
The TraceCPU inherits from BaseCPU as a result of which some methods need
to be defined. It has two port subclasses inherited from MasterPort for
instruction and data ports. It issues the memory requests deducing the
timing from the trace and without performing real execution of micro-ops.
As soon as the last dependency for an instruction is complete,
its computational delay, also provided in the input trace is added. The
dependency-free nodes are maintained in a list, called 'ReadyList',
ordered by ready time. Instructions which depend on load stall until the
responses for read requests are received thus achieving elastic replay. If
the dependency is not found when adding a new node, it is assumed complete.
Thus, if this node is found to be completely dependency-free its issue time is
calculated and it is added to the ready list immediately. This is encapsulated
in the subclass ElasticDataGen.
If ready nodes are issued in an unconstrained way there can be more nodes
outstanding which results in divergence in timing compared to the O3CPU.
Therefore, the Trace CPU also models hardware resources. A sub-class to model
hardware resources is added which contains the maximum sizes of load buffer,
store buffer and ROB. If resources are not available, the node is not issued.
The 'depFreeQueue' structure holds nodes that are pending issue.
Modeling the ROB size in the Trace CPU as a resource limitation is arguably the
most important parameter of all resources. The ROB occupancy is estimated using
the newly added field 'robNum'. We need to use ROB number as sequence number is
at times much higher due to squashing and trace replay is focused on correct
path modeling.
A map called 'inFlightNodes' is added to track nodes that are not only in
the readyList but also load nodes that are executed (and thus removed from
readyList) but are not complete. ReadyList handles what and when to execute
next node while the inFlightNodes is used for resource modelling. The oldest
ROB number is updated when any node occupies the ROB or when an entry in the
ROB is released. The ROB occupancy is equal to the difference in the ROB number
of the newly dependency-free node and the oldest ROB number in flight.
If no node dependends on a non load/store node then there is no reason to track
it in the dependency graph. We filter out such nodes but count them and add a
weight field to the subsequent node that we do include in the trace. The weight
field is used to model ROB occupancy during replay.
The depFreeQueue is chosen to be FIFO so that child nodes which are in
program order get pushed into it in that order and thus issued in the in
program order, like in the O3CPU. This is also why the dependents is made a
sequential container, std::set to std::vector. We only check head of the
depFreeQueue as nodes are issued in order and blocking on head models that
better than looping the entire queue. An alternative choice would be to inspect
top N pending nodes where N is the issue-width. This is left for future as the
timing correlation looks good as it is.
At the start of an execution event, first we attempt to issue such pending
nodes by checking if appropriate resources have become available. If yes, we
compute the execute tick with respect to the time then. Then we proceed to
complete nodes from the readyList.
When a read response is received, sometimes a dependency on it that was
supposed to be released when it was issued is still not released. This occurs
because the dependent gets added to the graph after the read was sent. So the
check is made less strict and the dependency is marked complete on read
response instead of insisting that it should have been removed on read sent.
There is a check for requests spanning two cache lines as this condition
triggers an assert fail in the L1 cache. If it does then truncate the size
to access only until the end of that line and ignore the remainder.
Strictly-ordered requests are skipped and the dependencies on such requests
are handled by simply marking them complete immediately.
The simulated seconds can be calculated as the difference between the
final_tick stat and the tickOffset stat. A CountedExitEvent that contains
a static int belonging to the Trace CPU class as a down counter is used to
implement multi Trace CPU simulation exit.
The elastic trace is a type of probe listener and listens to probe points
in multiple stages of the O3CPU. The notify method is called on a probe
point typically when an instruction successfully progresses through that
stage.
As different listener methods mapped to the different probe points execute,
relevant information about the instruction, e.g. timestamps and register
accesses, are captured and stored in temporary InstExecInfo class objects.
When the instruction progresses through the commit stage, the timing and the
dependency information about the instruction is finalised and encapsulated in
a struct called TraceInfo. TraceInfo objects are collected in a list instead
of writing them out to the trace file one a time. This is required as the
trace is processed in chunks to evaluate order dependencies and computational
delay in case an instruction does not have any register dependencies. By this
we achieve a simpler algorithm during replay because every record in the
trace can be hooked onto a record in its past. The instruction dependency
trace is written out as a protobuf format file. A second trace containing
fetch requests at absolute timestamps is written to a separate protobuf
format file.
If the instruction is not executed then it is not added to the trace.
The code checks if the instruction had a fault, if it predicated
false and thus previous register values were restored or if it was a
load/store that did not have a request (e.g. when the size of the
request is zero). In all these cases the instruction is set as
executed by the Execute stage and is picked up by the commit probe
listener. But a request is not issued and registers are not written.
So practically, skipping these should not hurt the dependency modelling.
If squashing results in squashing younger instructions, it may happen that
the squash probe discards the inst and removes it from the temporary
store but execute stage deals with the instruction in the next cycle which
results in the execute probe seeing this inst as 'new' inst. A sequence
number of the last processed trace record is used to trap these cases and
not add to the temporary store.
The elastic instruction trace and fetch request trace can be read in and
played back by the TraceCPU.
This patch adds probe points in Fetch, IEW, Rename and Commit stages as follows.
A probe point is added in the Fetch stage for probing when a fetch request is
sent. Notify is fired on the probe point when a request is sent succesfully in
the first attempt as well as on a retry attempt.
Probe points are added in the IEW stage when an instruction begins to execute
and when execution is complete. This points can be used for monitoring the
execution time of an instruction.
Probe points are added in the Rename stage to probe renaming of source and
destination registers and when there is squashing. These probe points can be
used to track register dependencies and remove when there is squashing.
A probe point for squashing is added in Commit to probe squashed instructions.
The gem5's current PCI host functionality is very ad hoc. The current
implementations require PCI devices to be hooked up to the
configuration space via a separate configuration port. Devices query
the platform to get their config-space address range. Un-mapped parts
of the config space are intercepted using the XBar's default port
mechanism and a magic catch-all device (PciConfigAll).
This changeset redesigns the PCI host functionality to improve code
reuse and make config-space and interrupt mapping more
transparent. Existing platform code has been updated to use the new
PCI host and configured to stay backwards compatible (i.e., no
guest-side visible changes). The current implementation does not
expose any new functionality, but it can easily be extended with
features such as automatic interrupt mapping.
PCI devices now register themselves with a PCI host controller. The
host controller interface is defined in the abstract base class
PciHost. Registration is done by PciHost::registerDevice() which takes
the device, its bus position (bus/dev/func tuple), and its interrupt
pin (INTA-INTC) as a parameter. The registration interface returns a
PciHost::DeviceInterface that the PCI device can use to query memory
mappings and signal interrupts.
The host device manages the entire PCI configuration space. Accesses
to devices decoded into the devices bus position and then forwarded to
the correct device.
Basic PCI host functionality is implemented in the GenericPciHost base
class. Most platforms can use this class as a basic PCI controller. It
provides the following functionality:
* Configurable configuration space decoding. The number of bits
dedicated to a device is a prameter, making it possible to support
both CAM, ECAM, and legacy mappings.
* Basic interrupt mapping using the interruptLine value from a
device's configuration space. This behavior is the same as in the
old implementation. More advanced controllers can override the
interrupt mapping method to dynamically assign host interrupts to
PCI devices.
* Simple (base + addr) remapping from the PCI bus's address space to
physical addresses for PIO, memory, and DMA.
The assert in lsq_unit_impl.hh line 963 needs pktPending to be initialized to
NULL (I got the assertion failure several times without the fix).
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
The last SimObject using the legacy serialize API with non-const
methods has now been transitioned to the new API. This changeset
removes the serializeOld() methods from the serialization base class
as they are no longer used.
