Only create a memory ordering violation when the value could have changed
between two subsequent loads, instead of just when loads go out-of-order
to the same address. While not very common in the case of Alpha, with
an architecture with a hardware table walker this can happen reasonably
frequently beacuse a translation will miss and start a table walk and
before the CPU re-schedules the faulting instruction another one will
pass it to the same address (or cache block depending on the dendency
checking).
This patch has been tested with a couple of self-checking hand crafted
programs to stress ordering between two cores.
The performance improvement on SPEC benchmarks can be substantial (2-10%).
So a mips-cross-gdb can connect with gem5(MIPS_SE), and do some remote
debugging.
Testing:
Build gem5 for MIPS_SE and make gem5 wait at beginning:
modify "rgdb_wait = -1" to "rgdb_wait = 0" in src/sim/system.cc;
scons build/MIPS_SE/gem5.opt CPU_MODELS=O3CPU
----
Build GDB-7.3 mips-cross:
./configure --target=mips-linux-gnu --prefix=xxx/gdb-7.3-install/
make
make install
----
Run:
./build/MIPS_SE/gem5.opt configs/example/se.py --detailed --caches
./mips-linux-gnu-gdb xxx/gem5/tests/test-progs/hello/bin/mips/linux/hello
(gdb) target remote :7000
(gdb) info registers
(gdb) disassemble
(gdb) si
(gdb) break main
(gdb) c
(gdb) quit
Testing done.
Having two StaticInst classes, one nominally ISA dependent and the other ISA
dependent, has not been historically useful and makes the StaticInst class
more complicated that it needs to be. This change merges StaticInstBase into
StaticInst.
This change pulls the instruction decoding machinery (including caches) out of
the StaticInst class and puts it into its own class. This has a few intrinsic
benefits. First, the StaticInst code, which has gotten to be quite large, gets
simpler. Second, the code that handles decode caching is now separated out
into its own component and can be looked at in isolation, making it easier to
understand. I took the opportunity to restructure the code a bit which will
hopefully also help.
Beyond that, this change also lays some ground work for each ISA to have its
own, potentially stateful decode object. We'd be able to include less
contextualizing information in the ExtMachInst objects since that context
would be applied at the decoder. Also, the decoder could "know" ahead of time
that all the instructions it's going to see are going to be, for instance, 64
bit mode, and it will have one less thing to check when it decodes them.
Because the decode caching mechanism has been separated out, it's now possible
to have multiple caches which correspond to different types of decoding
context. Having one cache for each element of the cross product of different
configurations may become prohibitive, so it may be desirable to clear out the
cache when relatively static state changes and not to have one for each
setting.
Because the decode function is no longer universally accessible as a static
member of the StaticInst class, a new function was added to the ThreadContexts
that returns the applicable decode object.
Do some minor cleanup of some recently added comments, a warning, and change
other instances of stack extension to be like what's now being done for x86.
The way flag bits were being set for microops in x86 ended up implicitly
calling the bitset constructor which was truncating flags beyond the width of
an unsigned long. This change sets the bits in chunks which are always small
enough to avoid being truncated. On 64 bit machines this should reduce to be
the same as before, and on 32 bit machines it should work properly and not be
unreasonably inefficient.
When an instruction is translated in the x86 TLB, a variable called
delayedResponse is passed back and forth which tracks whether a translation
could be completed immediately, or if there's going to be callback that will
finish things up. If a read was to the internal memory space, memory mapped
registers used to implement things like MSRs, the function hadn't yet gotten
to where delayedResponse was set to false, it's default. That meant that the
value was never set, and the TLB could start waiting for a callback that would
never come. This change simply moves the assignment to above where control
can divert to translateInt().
Nothing big here, but when you have an address that is not in the page table request to be allocated, if it falls outside of the maximum stack range all you get is a page fault and you don't know why. Add a little warn() to explain it a bit. Also add some comments and alter logic a little so that you don't totally ignore the return value of checkAndAllocNextPage().
There are a set of locations is the linux kernel that are managed via
cache maintence instructions until all processors enable their MMUs & TLBs.
Writes to these locations are manually flushed from the cache to main
memory when the occur so that cores operating without their MMU enabled
and only issuing uncached accesses can receive the correct data. Unfortuantely,
gem5 doesn't support any kind of software directed maintence of the cache.
Until such time as that support exists this patch marks the specific cache blocks
that need to be coherent as non-cacheable until all CPUs enable their MMU and
thus allows gem5 to boot MP systems with caches enabled (a requirement for
booting an O3 cpu and thus an O3 CPU regression).
SEV instructions were originally implemented to cause asynchronous squashes
via the generateTCSquash() function in the O3 pipeline when updating the
SEV_MAILBOX miscReg. This caused race conditions between CPUs in an MP system
that would lead to a pipeline either going inactive indefinitely or not being
able to commit squashed instructions. Fixed SEV instructions to behave like
interrupts and cause synchronous sqaushes inside the pipeline, eliminating
the race conditions. Also fixed up the semantics of the WFE instruction to
behave as documented in the ARMv7 ISA description to not sleep if SEV_MAILBOX=1
or unmasked interrupts are pending.
Control register operands are set up so that writing to them is serialize
after, serialize before, and non-speculative. These are probably overboard,
but they should usually be safe. Unfortunately there are times when even these
aren't enough. If an instruction modifies state that affects fetch, later
serialized instructions which come after it might have already gone through
fetch and decode by the time it commits. These instructions may have been
translated incorrectly or interpretted incorrectly and need to be destroyed.
This change modifies instructions which will or may have this behavior so that
they use the IsSquashAfter flag when necessary.
SWP and SWPB now throw an undefined instruction exception if
SCTLR.SW == 0. This also required the MIDR to be changed
slightly so programs can correctly determine that gem5 supports
the ARM v7 behavior of SWP/SWPB (in ARM v6, SWP/SWPB were
deprecated, but not disabled at CPU startup).
Adds MISCREG_ID_MMFR2 and removes break on access to MISCREG_CLIDR. Both
registers now return values that are consistent with current ARM
implementations.
This patch implements the copyRegs() function for the x86 architecture.
The patch assumes that no side effects other than TLB invalidation need
to be considered while copying the registers. This may not hold true in
future.
change hwrei back to being a non-control instruction so O3-FS mode will work
add squash in inorder that will catch a hwrei (or any other genric instruction)
that isnt a control inst but changes the PC. Additional testing still needs to be done
for inorder-FS mode but this change will free O3 development back up in the interim
This makes it possible to use the grammar multiple times and use the multiple
instances concurrently. This makes implementing an include statement as part
of a grammar possible.
This change simplifies the code surrounding operand type handling and makes it
depend only on the ctype that goes with each operand type. Future changes will
allow defining operand types by their ctypes directly, convert the ISAs over
to that style of definition, and then remove support for the old style. These
changes are to make it easier to use non-builtin types like classes or
structures as the type for operands.
readBytes and writeBytes had the word "bytes" in their names because they
accessed blobs of bytes. This distinguished them from the read and write
functions which handled higher level data types. Because those functions don't
exist any more, this change renames readBytes and writeBytes to more general
names, readMem and writeMem, which reflect the fact that they are how you read
and write memory. This also makes their names more consistent with the
register reading/writing functions, although those are still read and set for
some reason.
The DTB expects the correct PC in the ThreadContext
but how if the memory accesses are speculative? Shouldn't
we send along the requestor's PC to the translate functions?
this always changes the PC and is basically an impromptu branch instruction. why
not speculate on this instead of always be forced to mispredict/squash after the
hwrei gets resolved?
The InOrder model needs this marked as "isControl" so it knows to update the PC
after the ALU executes it. If this isnt marked as control, then it's going to
force the model to check the PC of every instruction at commit (what O3 does?),
and that would be a wasteful check for a very high percentage of instructions.
Instead of clearing the entire TLB on initialization and flush, the code was
clearing only one element. This patch corrects the memsets in the init and
flush routines.
this flag is only used for early branch resolution in the O3 model (of pc-relative branches)
but this isnt cleanly working even when the branch target code is added for sparc. For now,
we'll ignore this optimization and add a todo in the SPARC ISA for future developers
Add a few constants and functions that the InOrder model wants for SPARC.
* * *
sparc: add eaComp function
InOrder separates the address generation from the actual access so give
Sparc that functionality
* * *
sparc: add control flags for branches
branch predictors and other cpu model functions need to know specific information
about branches, so add the necessary flags here
The regular expressions matching filenames in the ##include directives and the
internally generated ##newfile directives where only looking for filenames
composed of alpha numeric characters, periods, and dashes. In Unix/Linux, the
rules for what characters can be in a filename are much looser than that. This
change replaces those expressions with ones that look for anything other than
a quote character. Technically quote characters are allowed as well so we
should allow escaping them somehow, but the additional complexity probably
isn't worth it.
We were getting a spurious warning in the regressions that turned
out to be due to having the wrong value for TGT_MAP_ANONYMOUS for
Power Linux, but in the process of tracking it down I ended up
doing some cleanup of the mmap handling in general.
A significant contributor to the need for adoptOrphanParams()
is the practice of appending to SimObjectVectors which have
already been assigned as children. This practice sidesteps the
assignment operation for those appended SimObjects, which is
where parent/child relationships are typically established.
This patch reworks the config scripts that use append() on
SimObjectVectors, which all happen to be in the x86 system
configuration. At some point in the future, I hope to make
SimObjectVectors immutable (by deriving from tuple rather than
list), at which time this patch will be necessary for correct
operation. For now, it just avoids some of the warning
messages that get printed in adoptOrphanParams().
This patch fixes two problems with the O3 cpu model. The first is an issue
with an instruction fetch causing a fault on the next address while the
current macro-op is being issued. This happens when the micro-ops exceed
the fetch bandwdith and then on the next cycle the fetch stage attempts
to issue a request to the next line while it still has micro-ops to issue
if the next line faults a fault is attached to a micro-op in the currently
executing macro-op rather than a "nop" from the next instruction block.
This leads to an instruction incorrectly faulting when on fetch when
it had no reason to fault.
A similar problem occurs with interrupts. When an interrupt occurs the
fetch stage nominally stops issuing instructions immediately. This is incorrect
in the case of a macro-op as the current location might not be interruptable.
This change further eliminates cases where condition codes were being read
just so they could be written without change because the instruction in
question was supposed to preserve them. This is done by creating the condition
code code based on the input rather than just doing a simple substitution.
If one of the condition codes isn't being used in the execution we should only
read it if the instruction might be dependent on it. With the preeceding changes
there are several more cases where we should dynamically pick instead of assuming
as we did before.
Break up the condition code bits into NZ, C, V registers. These are individually
written and this removes some incorrect dependencies between instructions.
Move the saturating bit (which is also saturating) from the renamed register
that holds the flags to the CPSR miscreg and adds a allows setting it in a
similar way to the FP saturating registers. This removes a dependency in
instructions that don't write, but need to preserve the Q bit.
This change splits out the condcodes from being one monolithic register
into three blocks that are updated independently. This allows CPUs
to not have to do RMW operations on the flags registers for instructions
that don't write all flags.
Debug flags are ExecUser, ExecKernel, and ExecAsid. ExecUser and
ExecKernel are set by default when Exec is specified. Use minus
sign with ExecUser or ExecKernel to remove user or kernel tracing
respectively.
Add registers and components to better support the VersatileEB board.
Made the MIDR and SYS_ID register parameters to ArmSystem and RealviewCtrl
respectively.
This change makes the decoder figure out if an instruction that only supports
memory is using a register encoding and decodes directly to "Unknown" which will
behave appropriately. This prevents other parts of the instruction creation
process from seeing the mismatch and asserting.
At the same time, rename the trace flags to debug flags since they
have broader usage than simply tracing. This means that
--trace-flags is now --debug-flags and --trace-help is now --debug-help
This change fixes a small bug in the arm copyRegs() code where some registers
wouldn't be copied if the processor was in a mode other than MODE_USER.
Additionally, this change simplifies the way the O3 switchCpu code works by
utilizing TheISA::copyRegs() to copy the required context information
rather than the adhoc copying that goes on in the CPU model. The current code
makes assumptions about the visibility of int and float registers that aren't
true for all architectures in FS mode.
***
(1): get rid of expandForMT function
MIPS is the only ISA that cares about having a piece of ISA state integrate
multiple threads so add constants for MIPS and relieve the other ISAs from having
to define this. Also, InOrder was the only core that was actively calling
this function
* * *
(2): get rid of corespecific type
The CoreSpecific type was used as a proxy to pass in HW specific params to
a MIPS CPU, but since MIPS FS hasnt been touched for awhile, it makes sense
to not force every other ISA to use CoreSpecific as well use a special
reset function to set it. That probably should go in a PowerOn reset fault
anyway.
The ISAR registers describe which features the processor supports.
Transcribe the values listed in section B5.2.5 of the ARM ARM
into the registers as read-only values
This change speeds up booting, especially in MP cases, by not executing
udelay() on the core but instead skipping ahead tha amount of time that is being
delayed.
This patch prevents not executed conditional instructions marked as
IsQuiesce from stalling the pipeline indefinitely. If the instruction
is not executed the quiesceSkip psuedoinst is called which schedules a
wakes up call to the fetch stage.
This changes the RFE macroop into 3 microops:
URa = [sp]; URb = [sp+4]; // load CPSR,PC values from stack
sp = sp + offset; // optionally auto-increment
PC = URa; CPSR = URb; // write to the PC and CPSR.
Importantly:
- writing to PC is handled in the last micro-op.
- loading occurs prior to state changes.
The internet says this instruction was created by accident when an Intel CPU
failed to decode x87 instructions properly. It's been documented on a few rare
occasions and has generally worked to ensure backwards compatability. One
source claims that the gcc toolchain is basically the only thing that emits
it, and that emulators/binary translators like qemu and bochs implement it.
We won't actually implement it here since we're hardly implementing any other
x87 instructions either. If we were to implement it, it would behave the same
as ffree but then also pop the register stack.
http://www.pagetable.com/?p=16
There may not be a formally correct spelling for the past tense of mmap, but
mmapped is the spelling Google doesn't try to autocorrect. This makes sense
because it mirrors the past tense of map->mapped and not the past tense of
cape->caped.
--HG--
rename : src/arch/alpha/mmaped_ipr.hh => src/arch/alpha/mmapped_ipr.hh
rename : src/arch/arm/mmaped_ipr.hh => src/arch/arm/mmapped_ipr.hh
rename : src/arch/mips/mmaped_ipr.hh => src/arch/mips/mmapped_ipr.hh
rename : src/arch/power/mmaped_ipr.hh => src/arch/power/mmapped_ipr.hh
rename : src/arch/sparc/mmaped_ipr.hh => src/arch/sparc/mmapped_ipr.hh
rename : src/arch/x86/mmaped_ipr.hh => src/arch/x86/mmapped_ipr.hh
We only support EABI binaries, so there is no reason to support OABI syscalls.
The loader detects OABI calls and fatal() so there is no reason to even check
here.
The ARM performance counters are not currently supported by the model.
This patch interprets a 'reset performance counters' command to mean 'reset
the simulator statistics' instead.
In x86, 32 and 64 bit writes to registers in which registers appear to be 32 or
64 bits wide overwrite all bits of the destination register. This change
removes false dependencies in these cases where the previous value of a
register doesn't need to be read to write a new value. New versions of most
microops are created that have a "Big" suffix which simply overwrite their
destination, and the right version to use is selected during microop
allocation based on the selected data size.
This does not change the performance of the O3 CPU model significantly, I
assume because there are other false dependencies from the condition code bits
in the flags register.
These faults can panic/warn/warn_once, etc., instead of instructions doing
that themselves directly. That way, instructions can be speculatively
executed, and only if they're actually going to commit will their fault be
invoked and the panic, etc., happen.
When redirecting fetch to handle branches, the npc of the current pc state
needs to be left alone. This change makes the pc state record whether or not
the npc already reflects a real value by making it keep track of the current
instruction size, or if no size has been set.
Uncacheable requests were set as such only in atomic mode.
currState->delayed is checked in place of currState->timing for resetting
currState in atomic mode.
Some ISAs (like ARM) relies on hardware page table walkers. For those ISAs,
when a TLB miss occurs, initiateTranslation() can return with NoFault but with
the translation unfinished.
Instructions experiencing a delayed translation due to a hardware page table
walk are deferred until the translation completes and kept into the IQ. In
order to keep track of them, the IQ has been augmented with a queue of the
outstanding delayed memory instructions. When their translation completes,
instructions are re-executed (only their initiateAccess() was already
executed; their DTB translation is now skipped). The IEW stage has been
modified to support such a 2-pass execution.
JMP_FAR_I was unpacking its far pointer operand using sll instead of srl like
it should, and also putting the components in the wrong registers for use by
other microcode.
During iret access LDT/GDT at CPL0 rather than after transition to user mode
(if I'm reading the Intel IA-64 architecture spec correctly, the contents of
the descriptor table are read before the CPL is updated).
Move page table walker state to its own object type, and make the
walker instantiate state for each outstanding walk. By storing the
states in a queue, the walker is able to handle multiple outstanding
timing requests. Note that functional walks use separate state
elements.
Double packet delete problem is due to an interrupt device deleting a packet that the SimpleTimingPort also deletes. Since MessagePort descends from SimpleTimingPort, simply reimplement the failing code from SimpleTimingPort: recvTiming.
Any change of control flow now resets the itstate to 0 mask and 0 condition,
except where the control flow alteration write into the cpsr register. These
case, for example return from an iterrupt, require the predecoder to recover
the itstate.
As there is a window of opportunity between the return from an interrupt
changing the control flow at the head of the pipe and the commit of the update
to the CPSR, the predecoder needs to be able to grab the ITstate early. This
is now handled by setting the forcedItState inside a PCstate for the control
flow altering instruction.
That instruction will have the correct mask/cond, but will not have a valid
itstate until advancePC is called (note this happens to advance the execution).
When the new PCstate is copy constructed it gets the itstate cond/mask, and
upon advancing the PC the itstate becomes valid.
Subsequent advancing invalidates the state and zeroes the cond/mask. This is
handled in isolation for the ARM ISA and should have no impact on other ISAs.
Refer arch/arm/types.hh and arch/arm/predecoder.cc for the details.
