[RFC 8/9] RISC-V: KVM: Implement perf support

[Sean Christopherson]

On Mon, Jul 18, 2022, Atish Patra wrote:
> RISC-V SBI PMU & Sscofpmf ISA extension allows supporting perf in
> the virtualization enviornment as well. KVM implementation
> relies on SBI PMU extension for most of the part while traps
> & emulates the CSRs read for counter access.

For the benefit of non-RISCV people, the changelog (and documentation?) should
explain why RISC-V doesn't need to tap into kvm_register_perf_callbacks().
Presumably there's something in the "RISC-V SBI PMU & Sscofpmf ISA extension" spec
that allows hardware to differentiate between events that are for guest vs. host?