Ssdbltrp - VS mode double trap check

[lewislzh]

In Spike's double trap check for VS/S mode, the current code accesses state.nonvirtual_sstatus in VS mode and state.sstatus in S mode.
processor.cc#L447-L453
I think this reverses the intended access to the VS/S status registers, preventing the correct execution of double traps in VS mode.
Moreover, I think it might not be necessary to use curr_virt to select between VS and S status registers.
Spike inherently supports accessing sstatus based on the current virtualization mode, reading from either sstatus or vsstatus as appropriate.
Therefore, we might consider adjusting line 466 to: reg_t s = state.sstatus->read();

[aswaterman]

@ved-rivos can you take a look at this?

[ved-rivos]

I think this reverses the intended access to the VS/S status registers, preventing the correct execution of double traps in VS mode

Yes. Thanks for spotting that.

Therefore, we might consider adjusting line 466 to: reg_t s = state.sstatus->read();

I am not sure that is right. Please see use of nonvirtual_sstatus vs. sstatus in rest of the function.

I sent a PR #1804 to swap it. @aswaterman please let me know if its right to just use sstatus->read(). Will it resolve to the sstatus or vstatus internally?

[aswaterman]

@ved-rivos I'll follow up on the PR.

[ved-rivos]

@aswaterman - Thanks. I have updated the PR.