[0/3] target/riscv: Add support for 'B' extension

Message

Rob Bradford Jan. 9, 2024, 5:07 p.m. UTC

Add support for the new (fast track) 'B' extension [1] this extension
uses the misa.B bit to indicate that the Zba, Zbb and Zbs extensions are
present.

Since this extension is not yet frozen it is exposed via the 'x-b' cpu
option. The validation logic is based on the new approach taken for the
'G' extension. [2]

The specification handles backward compatability: The misa.B bit may be
set if Zba, Zbb and Zbs are present but in order to not break existing
systems the bit is not required to be set if they are present. As such
even though Zba, Zbb and Zbs default to on in QEMU this extension is not
enabled by default in any cpu other than the 'max' variant.

Cheers,

Rob

[1] - https://github.com/riscv/riscv-b
[2] - https://patchew.org/QEMU/[e-mail]/[e-mail]/

Rob Bradford (3):
  target/riscv: Add infrastructure for 'B' MISA extension
  target/riscv: Add step to validate 'B' extension
  target/riscv: Enable 'B' extension on max CPU type

 target/riscv/cpu.c         |  5 +++--
 target/riscv/cpu.h         |  1 +
 target/riscv/tcg/tcg-cpu.c | 37 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 40 insertions(+), 3 deletions(-)