We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.
Backports commit fcf5ef2ab52c621a4617ebbef36bf43b4003f4c0 from qemu
Define a new CPU definition supporting 24KEc cores, similar to
the existing 24Kc, but with added support for DSP instructions
and MIPS16e (and without FPU).
Backports commit e9deaad8a58c899dc32e9fdeff9e533070e79dca from qemu
MIPS64R6-generic gradually gets closer to I6400 CPU, feature-wise. Rename
it to make it clear which MIPS processor it is supposed to emulate.
Backports commit 8f95ad1c79b4166350b982a6defe0e21faa04dac from qemu
This patch implements read and write access rules for Mips floating
point control and status register (FCR31). The change can be divided
into following parts:
- Add fields that will keep FCR31's R/W bitmask in procesor
definitions and processor float_status structure.
- Add appropriate value for FCR31's R/W bitmask for each supported
processor.
- Add function for setting snan_bit_is_one, and integrate it in
appropriate places.
- Modify handling of CTC1 (case 31) instruction to use FCR31's R/W
bitmask.
- Modify handling user mode executables for Mips, in relation to the
bit EF_MIPS_NAN2008 from ELF header, that is in turn related to
reading and writing to FCR31.
- Modify gdb behavior in relation to FCR31.
Backports commit 599bc5e89c46f95f86ccad0d747d041c89a28806 from qemu
Function msa_reset() is updated so that flag snan_bit_is_one is
properly set to 0.
By applying this patch, a number of incorrect MSA behaviors that
require IEEE 754-2008 compliance will be fixed. Those are behaviors
that (up to the moment of applying this patch) did not get the desired
functionality from SoftFloat library with respect to distinguishing
between quiet and signaling NaN, getting default NaN values (both
quiet and signaling), establishing if a floating point number is NaN
or not, etc.
Two examples:
* FMAX, FMIN will now correctly detect and propagate NaNs.
* FCLASS.D ans FCLASS.S will now correcty detect NaN flavors
Backports commit 40bd6dd456e61a36e454fb9dd2cc739b67c224cf from qemu
This patch modifies SoftFloat library so that it can be configured in
run-time in relation to the meaning of signaling NaN bit, while, at the
same time, strictly preserving its behavior on all existing platforms.
Background:
In floating-point calculations, there is a need for denoting undefined or
unrepresentable values. This is achieved by defining certain floating-point
numerical values to be NaNs (which stands for "not a number"). For additional
reasons, virtually all modern floating-point unit implementations use two
kinds of NaNs: quiet and signaling. The binary representations of these two
kinds of NaNs, as a rule, differ only in one bit (that bit is, traditionally,
the first bit of mantissa).
Up to 2008, standards for floating-point did not specify all details about
binary representation of NaNs. More specifically, the meaning of the bit
that is used for distinguishing between signaling and quiet NaNs was not
strictly prescribed. (IEEE 754-2008 was the first floating-point standard
that defined that meaning clearly, see [1], p. 35) As a result, different
platforms took different approaches, and that presented considerable
challenge for multi-platform emulators like QEMU.
Mips platform represents the most complex case among QEMU-supported
platforms regarding signaling NaN bit. Up to the Release 6 of Mips
architecture, "1" in signaling NaN bit denoted signaling NaN, which is
opposite to IEEE 754-2008 standard. From Release 6 on, Mips architecture
adopted IEEE standard prescription, and "0" denotes signaling NaN. On top of
that, Mips architecture for SIMD (also known as MSA, or vector instructions)
also specifies signaling bit in accordance to IEEE standard. MSA unit can be
implemented with both pre-Release 6 and Release 6 main processor units.
QEMU uses SoftFloat library to implement various floating-point-related
instructions on all platforms. The current QEMU implementation allows for
defining meaning of signaling NaN bit during build time, and is implemented
via preprocessor macro called SNAN_BIT_IS_ONE.
On the other hand, the change in this patch enables SoftFloat library to be
configured in run-time. This configuration is meant to occur during CPU
initialization, at the moment when it is definitely known what desired
behavior for particular CPU (or any additional FPUs) is.
The change is implemented so that it is consistent with existing
implementation of similar cases. This means that structure float_status is
used for passing the information about desired signaling NaN bit on each
invocation of SoftFloat functions. The additional field in float_status is
called snan_bit_is_one, which supersedes macro SNAN_BIT_IS_ONE.
IMPORTANT:
This change is not meant to create any change in emulator behavior or
functionality on any platform. It just provides the means for SoftFloat
library to be used in a more flexible way - in other words, it will just
prepare SoftFloat library for usage related to Mips platform and its
specifics regarding signaling bit meaning, which is done in some of
subsequent patches from this series.
Further break down of changes:
1) Added field snan_bit_is_one to the structure float_status, and
correspondent setter function set_snan_bit_is_one().
2) Constants <float16|float32|float64|floatx80|float128>_default_nan
(used both internally and externally) converted to functions
<float16|float32|float64|floatx80|float128>_default_nan(float_status*).
This is necessary since they are dependent on signaling bit meaning.
At the same time, for the sake of code cleanup and simplicity, constants
<floatx80|float128>_default_nan_<low|high> (used only internally within
SoftFloat library) are removed, as not needed.
3) Added a float_status* argument to SoftFloat library functions
XXX_is_quiet_nan(XXX a_), XXX_is_signaling_nan(XXX a_),
XXX_maybe_silence_nan(XXX a_). This argument must be present in
order to enable correct invocation of new version of functions
XXX_default_nan(). (XXX is <float16|float32|float64|floatx80|float128>
here)
4) Updated code for all platforms to reflect changes in SoftFloat library.
This change is twofolds: it includes modifications of SoftFloat library
functions invocations, and an addition of invocation of function
set_snan_bit_is_one() during CPU initialization, with arguments that
are appropriate for each particular platform. It was established that
all platforms zero their main CPU data structures, so snan_bit_is_one(0)
in appropriate places is not added, as it is not needed.
[1] "IEEE Standard for Floating-Point Arithmetic",
IEEE Computer Society, August 29, 2008.
Backports commit af39bc8c49224771ec0d38f1b693ea78e221d7bc from qemu
MIPS Release 6 and MIPS SIMD Architecture make it mandatory to have IEEE
754-2008 FPU which is indicated by CP1 FIR.HAS2008, FCSR.ABS2008 and
FCSR.NAN2008 bits set to 1.
In QEMU we still keep these bits cleared as there is no 2008-NaN support.
However, this now causes problems preventing from running R6 Linux with
the v4.5 kernel. Kernel refuses to execute 2008-NaN ELFs on a CPU
whose FPU does not support 2008-NaN encoding:
(...)
VFS: Mounted root (ext4 filesystem) readonly on device 8:0.
devtmpfs: mounted
Freeing unused kernel memory: 256K (ffffffff806f0000 - ffffffff80730000)
request_module: runaway loop modprobe binfmt-464c
Starting init: /sbin/init exists but couldn't execute it (error -8)
request_module: runaway loop modprobe binfmt-464c
Starting init: /bin/sh exists but couldn't execute it (error -8)
Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.
Therefore always indicate presence of 2008-NaN support in R6 as well as in
R5+MSA CPUs, even though this feature is not yet supported by MIPS in QEMU.
Backports commit ba5c79f26221c0fd7139c883a34a4e75d993f732 from qemu
The MAAR register is a read/write register included in Release 5
of the architecture that defines the accessibility attributes of
physical address regions. In particular, MAAR defines whether an
instruction fetch or data load can speculatively access a memory
region within the physical address bounds specified by MAAR.
As QEMU doesn't do speculative access, hence this patch only
provides ability to access the registers.
Backports commit f6d4dd810983fdf3d1c9fb81838167efef63d1c8 from qemu
Indicate that in the MIPS64R6-generic CPU the memory-mapped
Global Configuration Register Space is implemented.
Backports commit a9a95061715ca09abff56a3f239f704c410912c2 from qemu
MIPS Release 6 provides multi-threading features which replace
pre-R6 MT Module. CP0.Config3.MT is always 0 in R6, instead there is new
CP0.Config5.VP (Virtual Processor) bit which indicates presence of
multi-threading support which includes CP0.GlobalNumber register and
DVP/EVP instructions.
Backports commit 01bc435b44b8802cc4697faa07d908684afbce4e from qemu
Set Config5.XNP for R6 cores to indicate the extended LL/SC family
of instructions NOT present.
Backports commit 35ac9e342e008e3d47ef18d33a6977fdb99de9cd from qemu
As full specification of P5600 is available, mips32r5-generic should
be renamed to P5600 and corrected as its intention.
Correct PRid and detail of configuration.
Features which are not currently supported are described as FIXME.
Fix Config.MM bit location
Backports commit aff2bc6dc6d839caf6df0900437cc2cc9e180605 from qemu
Fix core configuration for MIPS64R6-generic to make it as close as
I6400.
I6400 core has 48-bit of Virtual Address available (SEGBITS).
MIPS SIMD Architecture is available.
Rearrange order of bits to match the specification.
Backports commit 4dc89b782095d7a0b919fafd7b1322b3cb1279f1 from qemu
Define a new CPU definition supporting MIPS32 Release 6 ISA and
microMIPS32 Release 6 ISA.
Backports commit 4b3bcd016d83cc75f6a495c1db54b6c77f037adc from qemu
PABITS are not hardcoded to 36 bits and we do not model 59 PABITS (which is
the architectural limit) in QEMU.
Backports commit 28b027d5b63c7550c7390041d6dd50948c8f55b8 from qemu
This relatively small architectural feature adds the following:
FIR.FREP: Read-only. If FREP=1, then Config5.FRE and Config5.UFE are
available.
Config5.FRE: When enabled all single-precision FP arithmetic instructions,
LWC1/LWXC1/MTC1, SWC1/SWXC1/MFC1 cause a Reserved Instructions
exception.
Config5.UFE: Allows user to write/read Config5.FRE using CTC1/CFC1
instructions.
Enable the feature in MIPS64R6-generic CPU.
Backports commit 7c979afd11b09a16634699dd6344e3ba10c9677e from qemu
Save MSACSR state. Also remove fp_status, msa_fp_status, hflags and restore
them in post_load() from the architectural registers.
Float exception flags are not present in vmstate. Information they carry
is used only by softfloat caller who translates them into MIPS FCSR.Cause,
FCSR.Flags and then they are cleared. Therefore there is no need for saving
them in vmstate.
Backports commit 644511117e7ca9f26d633a59c202a297113a796c from qemu
Backports commits d75de74967f631a7d0b538d4b88f96f9c426bfe2, 6225a4a0e39cb24e7b9e1d4d2c1a3e6eaee18e85, and d2bfa6e6222baa0218bd0658499d38bac56ac34c from qemu
Add the M14K and M14Kc processors from MIPS Technologies that are the
original implementation of the microMIPS ISA. They are dual instruction
set processors, implementing both the microMIPS and the standard MIPSr32
ISA.
These processors correspond to the M4K and 4KEc CPUs respectively,
except with support for the microMIPS instruction set added, support for
the MCU ASE added and two extra interrupt lines, making a total of 8
hardware interrupts plus 2 software interrupts. The remaining parts of
the microarchitecture, in particular the pipeline, stayed unchanged.
The presence of the microMIPS ASE is is reflected in the configuration
added. We currently have no support for the MCU ASE, including in
particular the ACLR, ASET and IRET instructions in either encoding, and
we have no support for the extra interrupt lines, including bits in
CP0.Status and CP0.Cause registers, so these features are not marked,
making our support diverge from real hardware.
Backports commit 11f5ea105c06bec72e9bc9a700fa65d60afb5ec3 from qemu
Add the 5KEc and 5KEf processors from MIPS Technologies that are the
original implementation of the MIPS64r2 ISA.
Silicon for these processors has never been taped out and no soft cores
were released even. They do exist though, a CP0.PRId value has been
assigned and experimental RTLs produced at the time the MIPS64r2 ISA has
been finalized. The settings introduced here faithfully reproduce that
hardware.
As far the implementation goes these processors are the same as the 5Kc
and the 5Kf CPUs respectively, except implementing the MIPS64r2 rather
than the original MIPS64 instruction set. There must have been some
updates to the CP0 architecture as mandated by the ISA, such as the
addition of the EBase register, although I am not sure about the exact
details, no documentation has ever been produced for these processors.
The remaining parts of the microarchitecture, in particular the
pipeline, stayed unchanged. Or to put it another way, the difference
between a 5K and a 5KE CPU corresponds to one between a 4K and a 4KE
CPU, except for the 64-bit rather than 32-bit ISA.
Backports commit 36b86e0dc2be93fc538fe7e11e0fda1a198f0135 from qemu
