[PATCH v3 20/23] KVM: s390: arm64: Finalize page fault handling
From: Steffen Eiden
Date: Fri Nov 06 2026 - 11:16:11 EST
Replace the temporary -ENOEXEC returns of the arm64-on-s390 page fault
handling with exception injection into the guest, mirroring arm64's
kvm_handle_guest_abort().
Translation faults beyond the physical address range are injected as an
address size fault, while faults falling between the VM's IPA size and
that range are injected as a synchronous external abort. Instruction
aborts and stage-1 walk faults on host addresses that back no guest page
are injected as synchronous external aborts as well, and a
PGM-addressing from the fault-in path is injected as an address size
fault, the closest arm64 equivalent. Injected faults return 1 so the
vCPU re-enters the guest with the pending exception instead of exiting
to userspace.
Co-developed-by: Andreas Grapentin <gra@xxxxxxxxxxxxx>
Signed-off-by: Andreas Grapentin <gra@xxxxxxxxxxxxx>
Signed-off-by: Steffen Eiden <seiden@xxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm_host_arm64.h | 1 +
arch/s390/kvm/arm64/arm.c | 6 +++
arch/s390/kvm/arm64/mmu.c | 74 +++++++++++++++++++++++-----------
arch/s390/kvm/arm64/sys_regs.c | 4 ++
4 files changed, 62 insertions(+), 23 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host_arm64.h b/arch/s390/include/asm/kvm_host_arm64.h
index 79549434a1d6..20f51cf9ce37 100644
--- a/arch/s390/include/asm/kvm_host_arm64.h
+++ b/arch/s390/include/asm/kvm_host_arm64.h
@@ -426,5 +426,6 @@ static inline bool vgic_host_has_gicv5(void)
}
void kvm_adjust_pc(struct kvm_vcpu *vcpu);
+size_t kvm_parange_to_address_sanitized(u32 id_parange);
#endif /* ASM_KVM_HOST_ARM64_H */
diff --git a/arch/s390/kvm/arm64/arm.c b/arch/s390/kvm/arm64/arm.c
index 91e9f4a75ce7..b5a0f8c1e9a4 100644
--- a/arch/s390/kvm/arm64/arm.c
+++ b/arch/s390/kvm/arm64/arm.c
@@ -63,9 +63,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
static u64 kvm_max_guest_address(void)
{
+ u64 mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+ u64 id_pa_addr;
u64 max_addr;
+ id_pa_addr = kvm_parange_to_address_sanitized(
+ SYS_FIELD_GET(ID_AA64MMFR0_EL1, PARANGE, mmfr0));
+
max_addr = min_t(u64, TASK_SIZE_MAX, sclp.hamax);
+ max_addr = min_t(u64, max_addr, id_pa_addr);
max_addr = max_t(u64, max_addr, SZ_1G - 1);
return ALIGN_DOWN(max_addr + 1, SZ_1G) - 1;
}
diff --git a/arch/s390/kvm/arm64/mmu.c b/arch/s390/kvm/arm64/mmu.c
index 31e0d036896f..7a6f6ba326c1 100644
--- a/arch/s390/kvm/arm64/mmu.c
+++ b/arch/s390/kvm/arm64/mmu.c
@@ -16,7 +16,8 @@ static inline bool kvm_s390_cur_gmap_fault_is_write(struct kvm_vcpu *vcpu)
/*
* user_mem_abort() - handle a dat fault for the gmap of a vcpu
*
- * Return: 0 on success, < 0 in case of error.
+ * Return: 0 if the fault was resolved, 1 if an exception was injected into
+ * the guest; the caller resumes the vCPU in both cases. < 0 in case of error.
* Context: The mm lock must not be held before calling. May sleep.
*/
static int user_mem_abort(struct kvm_vcpu *vcpu, gpa_t fault_ipa,
@@ -32,12 +33,14 @@ 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;
}
@@ -70,6 +73,35 @@ static int kvm_handle_pic(struct kvm_vcpu *vcpu, bool *translation)
return 0;
}
+size_t kvm_parange_to_address_sanitized(u32 id_parange)
+{
+ static u32 ranges_map[8] = {
+ [ID_AA64MMFR0_EL1_PARANGE_32] = 32,
+ [ID_AA64MMFR0_EL1_PARANGE_36] = 36,
+ [ID_AA64MMFR0_EL1_PARANGE_40] = 40,
+ [ID_AA64MMFR0_EL1_PARANGE_42] = 42,
+ [ID_AA64MMFR0_EL1_PARANGE_44] = 44,
+ [ID_AA64MMFR0_EL1_PARANGE_48] = 48,
+ [ID_AA64MMFR0_EL1_PARANGE_52] = 52,
+ [ID_AA64MMFR0_EL1_PARANGE_56] = 56,
+ };
+ u32 parange;
+
+ /*
+ * Future values must be higher than we know already.
+ * See ARM DDI 0487C.a. Return a safe limit.
+ */
+ parange = ranges_map[min(id_parange, ID_AA64MMFR0_EL1_PARANGE_56)];
+ return BIT_ULL(parange);
+}
+
+static size_t kvm_get_pa_address(struct kvm *kvm)
+{
+ u32 id_parange = get_idreg_field_enum(kvm, ID_AA64MMFR0_EL1, PARANGE);
+
+ return kvm_parange_to_address_sanitized(id_parange);
+}
+
int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
{
struct kvm_memory_slot *memslot;
@@ -98,16 +130,17 @@ 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 the PA range programmed for the guest */
+ if (fault_ipa >= kvm_get_pa_address(vcpu->kvm)) {
+ kvm_inject_size_fault(vcpu);
+ return 1;
+ }
- if (fault_ipa >= vcpu->kvm->arch.guest_phys_size)
- return -ENOEXEC;
+ /* Falls between the IPA range and the PA range? */
+ if (fault_ipa >= vcpu->kvm->arch.guest_phys_size) {
+ fault_ipa |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
+ return kvm_inject_sea(vcpu, is_iabt, fault_ipa);
+ }
}
trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_esr(vcpu),
@@ -121,23 +154,18 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
write_fault = kvm_s390_cur_gmap_fault_is_write(vcpu);
if (kvm_is_error_hva(hva) || (write_fault && !writable)) {
- ret = -ENOEXEC;
/*
* 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/arch/s390/kvm/arm64/sys_regs.c b/arch/s390/kvm/arm64/sys_regs.c
index 417a05ce9015..951a02d89fc5 100644
--- a/arch/s390/kvm/arm64/sys_regs.c
+++ b/arch/s390/kvm/arm64/sys_regs.c
@@ -317,6 +317,10 @@ static int arm64_check_features(struct kvm_vcpu *vcpu,
if (SYS_FIELD_GET(ID_AA64MMFR0_EL1, PARANGE, val) >
SYS_FIELD_GET(ID_AA64MMFR0_EL1, PARANGE, host_val))
return -E2BIG;
+ if (kvm_parange_to_address_sanitized(
+ SYS_FIELD_GET(ID_AA64MMFR0_EL1, PARANGE, val)) <
+ vcpu->kvm->arch.guest_phys_size)
+ return -E2BIG;
break;
case SYS_CTR_EL0:
/* forbid upgrading from VIPT to PIPT */
--
2.56.0