KVM: RISC-V: Add CPU PM notifier for non-retention idle states

Register a CPU_PM notifier to restore hypervisor CSR content during CPU
non-retention idle states. When a CPU enters a deep idle state that
powers off the CPU domain, hypervisor CSRs and VS CSRs lose their state
and must be saved before entry and restored after exit.

This completes KVM's power management coverage for RISC-V:
- CPU hotplug: handled by kvm_online_cpu/kvm_offline_cpu (cpuhp callbacks)
- System suspend: handled by kvm_suspend/kvm_resume (syscore ops)
- CPU idle (retention): no action needed, CSRs are retained
- CPU idle (non-retention): handled by this CPU_PM notifier

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260810-kvm-cpu-pm-v5-1-6c9e4c95caf5@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>

0 files changed, 0 insertions, 0 deletions