target/riscv: update some macro

[zqb-all]

1. update RISCV_MAX_HARTS to 2^20 according to SPEC
2. remove RISCV_MAX_REGISTERS, it's not used anywhere anymore

Change-Id: Iadf0fa1ba3bbe5b9420b8430883e140db87f4f9e

[timsifive]

Have you checked that we correctly modify hartselhi where needed, and that the code to select multiple harts will also work with >1024 harts? (I mean by reading the code, making a test case for this would be hard.

[zqb-all]

Have you checked that we correctly modify hartselhi where needed

All the places that use hartsello now have hartselhi, so I think there's no problem

and that the code to select multiple harts will also work with >1024 harts?

https://github.com/riscv/riscv-openocd/blob/21d21408aa36ccb458ccfaad871f7dd1bb1f731a/src/target/riscv/riscv-013.c#L4450-L4453
The length of this array is variable and I think it need space from stack, if hart count is huge, maybe we should change it to get space from calloc.

[JanMatCodasip]

zqb-all: The length of this array is variable and I think it need space from stack, if hart count is huge, maybe we should change it to get space from calloc.

Agreed, I think using dynamically allocated memory (malloc, calloc) makes sense in that case.

[JanMatCodasip]

Overall, this looks all right to me.

As a last suggestion, I'd recommend to put assert(dm->hart_count > 0) to places where hart_count is used and expected to be already filled in.

That's because hart_count is set to -1 initially before the real count is known, but we do not wish to see the negative value anytime after the harts have been examined.

[zqb-all]

That's because hart_count is set to -1 initially before the real count is known, but we do not wish to see the negative value anytime after the harts have been examined.

There is a check in examine

https://github.com/riscv/riscv-openocd/blob/21d21408aa36ccb458ccfaad871f7dd1bb1f731a/src/target/riscv/riscv-013.c#L1840-L1843

[timsifive]

Looks good overall.