On Wed, Jul 19, 2023 at 07:15:09AM -0700, Sean Christopherson wrote: > On Wed, Jul 19, 2023, Yuan Yao wrote: > > On Tue, Jul 18, 2023 at 04:44:48PM -0700, Sean Christopherson wrote: > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > > index 90a0be261a5c..d2d3e083ec7f 100644 > > > --- a/include/linux/kvm_host.h > > > +++ b/include/linux/kvm_host.h > > > @@ -255,7 +255,9 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > > > int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu); > > > #endif > > > > > > -#ifdef KVM_ARCH_WANT_MMU_NOTIFIER > > > +struct kvm_gfn_range; > > > > Not sure why a declaration here, it's defined for ARCHs which defined > > KVM_ARCH_WANT_MMU_NOTIFIER before. > > The forward declaration exists to handle cases where CONFIG_KVM=n, specifically > arch/powerpc/include/asm/kvm_ppc.h's declaration of hooks to forward calls to > uarch modules: > > bool (*unmap_gfn_range)(struct kvm *kvm, struct kvm_gfn_range *range); > bool (*age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); > bool (*test_age_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); > bool (*set_spte_gfn)(struct kvm *kvm, struct kvm_gfn_range *range); > > Prior to using a Kconfig, a forward declaration wasn't necessary because > arch/powerpc/include/asm/kvm_host.h would #define KVM_ARCH_WANT_MMU_NOTIFIER even > if CONFIG_KVM=n. > > Alternatively, kvm_ppc.h could declare the struct. I went this route mainly to > avoid the possibility of someone encountering the same problem on a different > architecture. Ah I see, thanks for your explanation!
