[PATCH kernel v4] KVM: PPC: Make KVM_CAP_IRQFD_RESAMPLE support platform dependent

[Sean Christopherson <seanjc@google.com>]

+Michael and KVM s390 maintainers

On Tue, Oct 04, 2022, Alexey Kardashevskiy wrote:
> When introduced, IRQFD resampling worked on POWER8 with XICS. However
> KVM on POWER9 has never implemented it - the compatibility mode code
> ("XICS-on-XIVE") misses the kvm_notify_acked_irq() call and the native
> XIVE mode does not handle INTx in KVM at all.
> 
> This moved the capability support advertising to platforms and stops
> advertising it on XIVE, i.e. POWER9 and later.
> 
> This should cause no behavioural change for other architectures.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Acked-by: Nicholas Piggin <npiggin@gmail.com>
> Acked-by: Marc Zyngier <maz@kernel.org>
> ---

If no one objects, I'll grab this for 6.4 and route it through kvm-x86/generic.

> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index fb1490761c87..908ce8bd91c9 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -593,6 +593,12 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>                 break;
>  #endif
>
> +#ifdef CONFIG_HAVE_KVM_IRQFD
> +       case KVM_CAP_IRQFD_RESAMPLE:
> +               r = !xive_enabled();
> +               break;
> +#endif

@PPC folks, do you want to avoid the #ifdef?  If so, I can tweak to this when
applying.

	case KVM_CAP_IRQFD_RESAMPLE:
		r = IS_ENABLED(CONFIG_HAVE_KVM_IRQFD) && !xive_enabled();
		break;