[PATCH 0/8] RISC V partial support for 128-bit architecture

* [PATCH 0/8] RISC V partial support for 128-bit architecture
@ 2021-08-30 17:16 ` Frédéric Pétrot
  0 siblings, 0 replies; 8+ messages in thread
From: Frédéric Pétrot @ 2021-08-30 17:16 UTC (permalink / raw)
  To: qemu-devel, qemu-riscv
  Cc: philmd, bin.meng, richard.henderson, palmer, fabien.portas,
	alistair.francis, Frédéric Pétrot, alex.bennee

This series of patches aims at adding partial 128-bit support to the riscv
target, following the (unratified) RV128I specification, Chapter 7 of
riscv-spec document dated 20191214.
It provides support for all user integer (I) instructions and for an M
extension which follows the definition of the 32 and 64-bit specifications.
We also included minimal support for 128-bit csrs.
Among the csrs, we selected misa, to know the mxlen in which the processor
is, mtvec, mepc, mscratch and mstatus for minimal kernel development, and
satp to point to the page table.
We fallback on the 64-bit csrs for the others.

In the last patch, we propose a "natural" extension of the sv39 and sv48
virtual address modes using 16KB pages, that we believe suitable for
128-bit CPU workloads.

There are two strong assumptions in this implementation:
- the 64 upper bits of the addresses are irrelevant, be they virtual or
  physical, in order to use the existing address translation mechanism,
- the mxlen field stays hardwired, so there is no dynamic change in
  register size.

As no toolchain exists yet for this target, we wrote all our tests in asm
using macros expanding .insn directives.
We unit tested the behavior of the instructions, and wrote some simple
user level performance tests: on our examples the execution speed of the
128-bit version is between 1.2 to 5 time slower than its 32 and 64-bit
counterparts.

Thanks to Luc Michel for his advice in building the patches (although
all errors are ours.)

Frédéric Pétrot (8):
  target/riscv: Settings for 128-bit extension support
  target/riscv: 128-bit registers creation and access
  target/riscv: Addition of 128-bit ldu, lq and sq instructions
  target/riscv: 128-bit arithmetic and logic instructions
  target/riscv: 128-bit multiply and divide
  target/riscv: Support of compiler's 128-bit integer types
  target/riscv: 128-bit support for some csrs
  target/riscv: Support for 128-bit satp

 configs/devices/riscv128-softmmu/default.mak |   16 +
 configs/targets/riscv128-softmmu.mak         |    5 +
 gdb-xml/riscv-128bit-cpu.xml                 |   48 +
 gdb-xml/riscv-128bit-virtual.xml             |   12 +
 include/hw/riscv/sifive_cpu.h                |    4 +
 include/tcg/tcg-op.h                         |    1 +
 slirp                                        |    2 +-
 target/riscv/Kconfig                         |    3 +
 target/riscv/arch_dump.c                     |    3 +-
 target/riscv/cpu-param.h                     |   12 +-
 target/riscv/cpu.c                           |   51 +-
 target/riscv/cpu.h                           |   61 +
 target/riscv/cpu_bits.h                      |   12 +
 target/riscv/cpu_helper.c                    |   56 +-
 target/riscv/csr.c                           |  343 ++++-
 target/riscv/gdbstub.c                       |    3 +
 target/riscv/helper.h                        |   15 +
 target/riscv/insn16.decode                   |   33 +-
 target/riscv/insn32.decode                   |   25 +
 target/riscv/insn_trans/trans_rvd.c.inc      |   10 +-
 target/riscv/insn_trans/trans_rvf.c.inc      |    2 +-
 target/riscv/insn_trans/trans_rvi.c.inc      | 1209 +++++++++++++++++-
 target/riscv/insn_trans/trans_rvm.c.inc      |  456 ++++++-
 target/riscv/m128_helper.c                   |  349 +++++
 target/riscv/meson.build                     |    1 +
 target/riscv/op_helper.c                     |   60 +
 target/riscv/translate.c                     |  104 +-
 target/riscv/utils_128.h                     |  173 +++
 tcg/tcg-op.c                                 |    6 +
 29 files changed, 2990 insertions(+), 85 deletions(-)
 create mode 100644 configs/devices/riscv128-softmmu/default.mak
 create mode 100644 configs/targets/riscv128-softmmu.mak
 create mode 100644 gdb-xml/riscv-128bit-cpu.xml
 create mode 100644 gdb-xml/riscv-128bit-virtual.xml
 create mode 100644 target/riscv/m128_helper.c
 create mode 100644 target/riscv/utils_128.h

-- 
2.33.0

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