[PATCH 3/7] KVM: PPC: Explicitly force IPIs when directly kicking vCPUs

[Gautam Menghani]

On Wed, Oct 28, 2026 at 12:02:55PM -0700, Sean Christopherson wrote:
> Explicitly force an IPI when invoking kvm_vcpu_kick() directly instead of
> relying on kvm_arch_vcpu_should_kick() to unconditionally return 1/true.
> This will allow dropping kvm_arch_vcpu_should_kick() in favor of
> kvm_request_needs_ipi().
> 
> No functional change intended (1 || 1 == true).
> 
> Signed-off-by: Sean Christopherson <seanjc at google.com>
> ---
>  arch/powerpc/include/asm/kvm_ppc.h | 13 ++++++++++++-
>  arch/powerpc/kvm/book3s.c          |  4 ++--
>  arch/powerpc/kvm/book3s_pr.c       |  2 +-
>  arch/powerpc/kvm/booke.c           |  6 +++---
>  arch/powerpc/kvm/e500_emulate.c    |  2 +-
>  arch/powerpc/kvm/powerpc.c         |  2 +-
>  6 files changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 169ea6a7fbad..bbe7378ad0ef 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -30,6 +30,17 @@
>  #endif
>  #include <asm/inst.h>
>  
> +/*
> + * TODO: For unknown reasons, KVM PPC has historically ignored vcpu->mode when
> + *       determining if kicking a vCPU needs an IPI.  Either document why that
> + *       behavior is necessary, or drop this helper and the @force param from
> + *       __kvm_vcpu_kick().
> + */
> +static inline void kvmppc_vcpu_kick(struct kvm_vcpu *vcpu)
> +{
> +	__kvm_vcpu_kick(vcpu, false, true);
> +}
> +

AFAICS, there is no reason for PPC to always return 1. I was looking at
the old patches on mailing list and found this - https://lore.kernel.org/kvm/0FEE585F-5E21-47F2-A3F0-AD0DE05EBB43@suse.de

```
How about we return 1 for kvm_arch_vcpu_in_guest_mode() on !x86 always, just like it's done today basically? Then we can
worry about needless IPIs later and don't regress from the respective current kick implementations.
```

However, I'll do some testing and get back by mid next week to make sure
there are no suprises.


Thanks,
Gautam