In the Linux kernel, the following vulnerability has been resolved:

RISC-V: KVM: Write hgatp register with valid mode bits

According to the RISC-V Privileged Architecture Spec, when MODE=Bare
is selected,software must write zero to the remaining fields of hgatp.

We have detected the valid mode supported by the HW before, So using a
valid mode to detect how many vmid bits are supported.