Subject: [PATCH v1 26/26] KVM: s390: arm64: Finalize page fault handling

From: Steffen Eiden <[email-masked]>
Date: Fri, 29 May 2026 17:55:59 +0200

Complete the page fault handling implementation by replacing temporary
error returns with proper ARM64 exception injection.

Signed-off-by: Steffen Eiden <[email-masked]>
---
 arch/s390/kvm/arm64/mmu.c       | 62 ++++++++++++++++++++++-----------
 include/kvm/arm64/kvm_feature.h |  3 ++
 2 files changed, 44 insertions(+), 21 deletions(-)

diff --git a/arch/s390/kvm/arm64/mmu.c b/arch/s390/kvm/arm64/mmu.c
index 8759cbafbaff..4224503276fb 100644
--- a/arch/s390/kvm/arm64/mmu.c
+++ b/arch/s390/kvm/arm64/mmu.c
@@ -31,12 +31,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, gpa_t fault_ipa,
 	ret = kvm_s390_faultin_gfn(vcpu, NULL, &f);
 	if (ret <= 0)
 		return ret;
-	if (ret == PGM_ADDRESSING)
+	if (ret == PGM_ADDRESSING) {
 		/*
-		 * Without the relevant sysregs we cannot do anything for now.
-		 * Go back to userspace with an error. TODO sysreg handling
+		 * There is no page with the requested address. Inject size fault
+		 * which is the closest arm match to PGM-addressing
 		 */
-		return -ENOEXEC;
+		kvm_inject_size_fault(vcpu);
+		return 1;
+	}
 	KVM_BUG_ON(ret, vcpu->kvm);
 	return -EINVAL;
 }
@@ -69,6 +71,27 @@ static int kvm_handle_pic(struct kvm_vcpu *vcpu, bool *translation)
 	return 0;
 }
 
+static u32 kvm_get_pa_bits(struct kvm *kvm)
+{
+	u32 id_parange = get_idreg_field_enum(kvm, ID_AA64MMFR0_EL1, PARANGE);
+
+	switch (id_parange) {
+	case ID_AA64MMFR0_EL1_PARANGE_32: return 32;
+	case ID_AA64MMFR0_EL1_PARANGE_36: return 36;
+	case ID_AA64MMFR0_EL1_PARANGE_40: return 40;
+	case ID_AA64MMFR0_EL1_PARANGE_42: return 42;
+	case ID_AA64MMFR0_EL1_PARANGE_44: return 44;
+	case ID_AA64MMFR0_EL1_PARANGE_48: return 48;
+	case ID_AA64MMFR0_EL1_PARANGE_52: return 52;
+	case ID_AA64MMFR0_EL1_PARANGE_56: return 56;
+	}
+	/*
+	 * Future values must be higher than we know already.
+	 * See ARM DDI 0487C.a. Return a safe limit.
+	 */
+	return ID_AA64MMFR0_EL1_PARANGE_48;
+}
+
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 {
 	struct kvm_memory_slot *memslot;
@@ -98,16 +121,17 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 	}
 
 	if (translation) {
-		/*
-		 * For both cases:
-		 * Without the relevant sysregs we cannot do anything for now.
-		 * Go back to userspace with an error. TODO sysreg handling
-		 */
-		if (fault_ipa >= BIT_ULL(get_kvm_ipa_limit()))
-			return -ENOEXEC;
+		/* Beyond sanitised PA range (which is the IPA limit) */
+		if (fault_ipa >= BIT_ULL(kvm_get_pa_bits(vcpu->kvm))) {
+			kvm_inject_size_fault(vcpu);
+			return 1;
+		}
 
-		if (fault_ipa >= kvm_phys_size(vcpu->kvm))
-			return -ENOEXEC;
+		/* Falls between the IPA range and the PA range? */
+		if (fault_ipa >= kvm_phys_size(vcpu->kvm)) {
+			fault_ipa |= kvm_vcpu_get_hfar(vcpu) & GENMASK(11, 0);
+			return kvm_inject_sea(vcpu, is_iabt, fault_ipa);
+		}
 	}
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
@@ -123,18 +147,14 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 		 * The guest has put either its instructions or its page-tables
 		 * somewhere it shouldn't have. Userspace won't be able to do
 		 * anything about this (there's no syndrome for a start).
-		 *
-		 * Without the relevant sysregs we cannot do anything for now.
-		 * Go back to userspace with an error. TODO sysreg handling
 		 */
-		if (is_iabt)
+		if (is_iabt) {
+			ret = kvm_inject_sea_iabt(vcpu, kvm_vcpu_get_hfar(vcpu));
 			goto out_unlock;
+		}
 
 		if (kvm_vcpu_abt_iss1tw(vcpu)) {
-			/*
-			 * Without the relevant sysregs we cannot do anything for now.
-			 * Go back to userspace with an error. TODO sysreg handling
-			 */
+			ret = kvm_inject_sea_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
 			goto out_unlock;
 		}
 
diff --git a/include/kvm/arm64/kvm_feature.h b/include/kvm/arm64/kvm_feature.h
index 945abbbf1aa8..193c9ca7045f 100644
--- a/include/kvm/arm64/kvm_feature.h
+++ b/include/kvm/arm64/kvm_feature.h
@@ -47,6 +47,9 @@
 
 #define kvm_has_feat_enum(kvm, ...) __kvm_has_feat_enum(kvm, __VA_ARGS__)
 
+#define get_idreg_field_enum(kvm, id, fld)				\
+	SYS_FIELD_GET(id, fld, kvm_read_vm_id_reg((kvm), SYS_##id))
+
 /* Check for a given level of PAuth support */
 #define kvm_has_pauth(k, l)						\
 	({								\
-- 
2.53.0