[PATCH v2 5/5] KVM: arm64: Define FAR_MASK for fault IPA offset

[Fuad Tabba]

On Fri, 7 Nov 2025 at 23:12, Oliver Upton <oupton at kernel.org> wrote:
>
> On Thu, Nov 06, 2025 at 02:44:17PM +0000, Fuad Tabba wrote:
> > This 12-bit FAR mask is hard-coded as 'GENMASK(11, 0)' in several places
> > to reconstruct the full fault IPA.
> >
> > Define FAR_MASK for this value in the shared header and replace all
> > open-coded instances to improve readability.
> >
> > No functional change intended.
> >
> > Signed-off-by: Fuad Tabba <tabba at google.com>
> > ---
> >  arch/arm64/include/asm/kvm_arm.h         | 2 ++
> >  arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c | 2 +-
> >  arch/arm64/kvm/inject_fault.c            | 2 +-
> >  arch/arm64/kvm/mmu.c                     | 4 ++--
> >  4 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> > index 1da290aeedce..e995e9b3a0c4 100644
> > --- a/arch/arm64/include/asm/kvm_arm.h
> > +++ b/arch/arm64/include/asm/kvm_arm.h
> > @@ -343,6 +343,8 @@
> >  #define PAR_TO_HPFAR(par)            \
> >       (((par) & GENMASK_ULL(52 - 1, 12)) >> 8)
> >
> > +#define FAR_MASK GENMASK_ULL(11, 0)
> > +
>
> This seems really confusing to me, since FAR_MASK sounds like it
> represents the meaningful bits of FAR_ELx. Perhaps something like the
> following would better represent intent:
>
> #define FAR_TO_FIPA_OFFSET(far) ((far) & GENMASK_ULL(11, 0))

Sounds better. I'll change it.

Cheers,
/fuad

> Thanks,
> Oliver
>
> >  #define ECN(x) { ESR_ELx_EC_##x, #x }
> >
> >  #define kvm_arm_exception_class \
> > diff --git a/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c b/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> > index 78579b31a420..22898ed4dd6f 100644
> > --- a/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> > +++ b/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> > @@ -44,7 +44,7 @@ int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu)
> >
> >       /* Build the full address */
> >       fault_ipa  = kvm_vcpu_get_fault_ipa(vcpu);
> > -     fault_ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
> > +     fault_ipa |= kvm_vcpu_get_hfar(vcpu) & FAR_MASK;
> >
> >       /* If not for GICV, move on */
> >       if (fault_ipa <  vgic->vgic_cpu_base ||
> > diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
> > index dfcd66c65517..8ef3453696a2 100644
> > --- a/arch/arm64/kvm/inject_fault.c
> > +++ b/arch/arm64/kvm/inject_fault.c
> > @@ -258,7 +258,7 @@ void kvm_inject_size_fault(struct kvm_vcpu *vcpu)
> >       unsigned long addr, esr;
> >
> >       addr  = kvm_vcpu_get_fault_ipa(vcpu);
> > -     addr |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
> > +     addr |= kvm_vcpu_get_hfar(vcpu) & FAR_MASK;
> >
> >       __kvm_inject_sea(vcpu, kvm_vcpu_trap_is_iabt(vcpu), addr);
> >
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 7cc964af8d30..21a9442f9b1e 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -1959,7 +1959,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
> >
> >               /* Falls between the IPA range and the PARange? */
> >               if (fault_ipa >= BIT_ULL(VTCR_EL2_IPA(vcpu->arch.hw_mmu->vtcr))) {
> > -                     fault_ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
> > +                     fault_ipa |= kvm_vcpu_get_hfar(vcpu) & FAR_MASK;
> >
> >                       return kvm_inject_sea(vcpu, is_iabt, fault_ipa);
> >               }
> > @@ -2059,7 +2059,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
> >                * faulting VA. This is always 12 bits, irrespective
> >                * of the page size.
> >                */
> > -             ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
> > +             ipa |= kvm_vcpu_get_hfar(vcpu) & FAR_MASK;
> >               ret = io_mem_abort(vcpu, ipa);
> >               goto out_unlock;
> >       }
> > --
> > 2.51.2.1041.gc1ab5b90ca-goog
> >