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From:   Fuad Tabba <tabba@google.com>
Date:   Wed, 1 Nov 2023 12:51:19 +0000
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Subject: Re: [PATCH v13 05/35] KVM: PPC: Drop dead code related to KVM_ARCH_WANT_MMU_NOTIFIER
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
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On Fri, Oct 27, 2023 at 7:22=E2=80=AFPM Sean Christopherson <seanjc@google.=
com> wrote:
>
> Assert that both KVM_ARCH_WANT_MMU_NOTIFIER and CONFIG_MMU_NOTIFIER are
> defined when KVM is enabled, and return '1' unconditionally for the
> CONFIG_KVM_BOOK3S_HV_POSSIBLE=3Dn path.  All flavors of PPC support for K=
VM
> select MMU_NOTIFIER, and KVM_ARCH_WANT_MMU_NOTIFIER is unconditionally
> defined by arch/powerpc/include/asm/kvm_host.h.
>
> Effectively dropping use of KVM_ARCH_WANT_MMU_NOTIFIER will simplify a
> future cleanup to turn KVM_ARCH_WANT_MMU_NOTIFIER into a Kconfig, i.e.
> will allow combining all of the
>
>   #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
>
> checks into a single
>
>   #ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
>
> without having to worry about PPC's "bare" usage of
> KVM_ARCH_WANT_MMU_NOTIFIER.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---

Reviewed-by: Fuad Tabba <tabba@google.com>

Cheers,
/fuad

>  arch/powerpc/kvm/powerpc.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 7197c8256668..b0a512ede764 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -632,12 +632,13 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, l=
ong ext)
>                 break;
>  #endif
>         case KVM_CAP_SYNC_MMU:
> +#if !defined(CONFIG_MMU_NOTIFIER) || !defined(KVM_ARCH_WANT_MMU_NOTIFIER=
)
> +               BUILD_BUG();
> +#endif
>  #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
>                 r =3D hv_enabled;
> -#elif defined(KVM_ARCH_WANT_MMU_NOTIFIER)
> -               r =3D 1;
>  #else
> -               r =3D 0;
> +               r =3D 1;
>  #endif
>                 break;
>  #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> --
> 2.42.0.820.g83a721a137-goog
>