On Thu, Sep 01, 2022, Marc Zyngier wrote: > Sean, > > On Thu, 11 Aug 2022 18:39:53 +0100, > Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > +Will (for arm crud) > > When it comes to KVM/arm64, I'd appreciate if you could Cc me. Sorry, will do. > > arm64 is also quite evil and circumvents KVM's hardware enabling > > logic to some extent. kvm_arch_init() => init_subsystems() > > unconditionally enables hardware, and for pKVM _leaves_ hardware > > enabled. And then hyp_init_cpu_pm_notifier() disables/enables > > hardware across lower power enter+exit, except if pKVM is enabled. > > The icing on the cake is "disabling" hardware doesn't even do > > anything (AFAICT) if the kernel is running at EL2 (which I think is > > nVHE + not-pKVM?). > > In the cases where disabling doesn't do anything (which are the exact > opposite of the cases you describe), that's because there is > absolutely *nothing* to do: Yes, I know. > - If VHE, the kernel is the bloody hypervisor: disable virtualisation, > kill the kernel. > > - if pKVM, the kernel is basically a guest, and has no business > touching anything at all. > > So much the 'evil' behaviour. The colorful language is tongue-in-cheek. I get the impression that you feel I am attacking ARM. That is very much not what I intended. If anything, I'm attacking x86 for forcing its quirks on everyone else. What am trying to point out here is that ARM and other architectures are not well-served by KVM's current hardware enabling/disabling infrastructure. I am not saying that ARM is broken and needs to be fixed, I am saying that KVM is broken and needs to be fixed, and that ARM is a victim of KVM's x86-centric origins.
