Paolo Bonzini wrote:

... I guess this is the misunderstanding. I'm not proposing to delegate
the WFI trap to the guest, but rather *the WFI instruction*: HS-mode
could optionally let WFI run in VS-mode, even if it wouldn't complete
within a bounded time. This is because, if you don't overcommit CPUs,
there's no advantage in getting out of VS-mode and doing the wait for
interrupts in HS-mode.

Okay, I get it now. You're proposing we bring back hstatus.VTW,
the HS-mode analog to mstatus.TW. (We had the VTW bit originally in
hstatus, but dropped it long ago.)

Anyone else have an opinion about that?

- John Hauser

I wrote:

Okay, I get it now. You're proposing we bring back hstatus.VTW,
the HS-mode analog to mstatus.TW. (We had the VTW bit originally in
hstatus, but dropped it long ago.)

I've created a pull request for the RISC-V privileged manual:
https://github.com/riscv/riscv-isa-manual/pull/523

Comments welcome.

- John Hauser