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/20231218125334.37184-1-dbarb...@ventanamicro.com/20231218125334.37184-16-dbarb...@ventanamicro.com/ 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(-) -- 2.43.0
