KVM: arm64: Introduce helper to calculate fault IPA offset

This 12-bit FAR fault IPA offset mask is hard-coded as 'GENMASK(11, 0)'
in several places to reconstruct the full fault IPA.

Introduce FAR_TO_FIPA_OFFSET() to calculate this value in a shared
header and replace all open-coded instances to improve readability.

No functional change intended.

Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20251211104710.151771-5-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Fuad Tabba

arch/arm64/include/asm/kvm_arm.h

@@ -344,6 +344,8 @@
 #define PAR_TO_HPFAR(par)		\
 	(((par) & GENMASK_ULL(52 - 1, 12)) >> 8)
 
+#define FAR_TO_FIPA_OFFSET(far) ((far) & GENMASK_ULL(11, 0))
+
 #define ECN(x) { ESR_ELx_EC_##x, #x }
 
 #define kvm_arm_exception_class \

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 |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
 
 	/* If not for GICV, move on */
 	if (fault_ipa <  vgic->vgic_cpu_base ||

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 |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
 
 	__kvm_inject_sea(vcpu, kvm_vcpu_trap_is_iabt(vcpu), addr);
 

arch/arm64/kvm/mmu.c

@@ -2070,7 +2070,7 @@ 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 |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
 
 			return kvm_inject_sea(vcpu, is_iabt, fault_ipa);
 		}
@@ -2175,7 +2175,7 @@ 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 |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
 		ret = io_mem_abort(vcpu, ipa);
 		goto out_unlock;
 	}