Understanding hypervisor extension

[yf13]

I have some basic questions regarding hypervisor extension v1.0:

• Can we take virtualization mode as separate control in the hart? This means privilege mode value 2 is still reserved, the privilege mode value for both HS and VS are 1, and that for both U and VU are 0.

• Is there any way to learn current virtualzation mode of a hart from registers or debugging interfaces?

• Like we use mret/sret and ecall instructions to change privilege modes, how can we change the virtualizaton mode?

[aswaterman]

1. It is an orthogonal state, separate from mode.
2. Not from the current hart (by design). An external debugger can learn whatever it wants.
3. Read the hypervisor spec again.