[PATCH 1/1] target/riscv: enable floating point unit

[Heinrich Schuchardt]

On 18.09.24 15:56, Andrew Jones wrote:
> Thanks Heinrich, I had also forgotten that distinction. So the last
> question is whether or not we want to reset mstatus.FS to 1 instead of 3,
> as is done in this patch.
> 
> Thanks,
> drew


If the FD flag set to 3 (Dirty) indicates that "the corresponding state 
has potentially been modified since the last context save". Upon context 
switches the value of the floating point registers has to be saved.

The value 1 (Initial) implies that saving the registers on a context 
change is not needed.

3 (Dirty) is the safest choice. This is why OpenSBI is also using it.

For reference:

3.1.6.6. Extension Context Status in mstatus Register
The RISC-V Instruction Set Manual: Volume II - Privileged Architecture
Version 2024-04-11

Best regards

Heinrich