[PATCH v1 25/26] KVM: s390: arm64: Implement exception injection
From: Steffen Eiden
Date: Fri May 29 2026 - 12:47:47 EST
Add exception injection support for s390 KVM arm64 architecture. This
implements the core exception entry mechanism and fault injection
functions needed for proper guest exception handling.
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 | 2 +
arch/s390/kvm/arm64/Makefile | 1 +
arch/s390/kvm/arm64/arm.c | 15 +---
arch/s390/kvm/arm64/exception.c | 105 +++++++++++++++++++++++++
arch/s390/kvm/arm64/inject_fault.c | 72 ++++++++++++++++-
5 files changed, 182 insertions(+), 13 deletions(-)
create mode 100644 arch/s390/kvm/arm64/exception.c
diff --git a/arch/s390/include/asm/kvm_host_arm64.h b/arch/s390/include/asm/kvm_host_arm64.h
index cc457d69621c..34d131b36e70 100644
--- a/arch/s390/include/asm/kvm_host_arm64.h
+++ b/arch/s390/include/asm/kvm_host_arm64.h
@@ -373,4 +373,6 @@ static inline u64 kvm_sanitised_host_ftr_reg(u32 id)
return kvm_arm_host_sys_reg_by_id(id);
}
+void kvm_adjust_pc(struct kvm_vcpu *vcpu);
+
#endif /* ASM_KVM_HOST_ARM64_H */
diff --git a/arch/s390/kvm/arm64/Makefile b/arch/s390/kvm/arm64/Makefile
index bec24b60a071..9d6b7d5bf588 100644
--- a/arch/s390/kvm/arm64/Makefile
+++ b/arch/s390/kvm/arm64/Makefile
@@ -9,6 +9,7 @@ ccflags-y += -I $(src) -I$(srctree)/arch/s390/kvm/gmap -DKVM_S390_ARM64
kvm-arm64-obj := \
arm.o \
+ exception.o \
feature.o \
guest.o \
handle_exit.o \
diff --git a/arch/s390/kvm/arm64/arm.c b/arch/s390/kvm/arm64/arm.c
index 88b66552cff0..c62e50002628 100644
--- a/arch/s390/kvm/arm64/arm.c
+++ b/arch/s390/kvm/arm64/arm.c
@@ -350,19 +350,11 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
return 0;
}
-static void adjust_pc(struct kvm_vcpu *vcpu)
-{
- if (vcpu_get_flag(vcpu, INCREMENT_PC)) {
- kvm_skip_instr(vcpu);
- vcpu_clear_flag(vcpu, INCREMENT_PC);
- }
-}
-
static void arm_vcpu_run(struct kvm_vcpu *vcpu)
{
struct kvm_sae_block *sae_block = &vcpu->arch.sae_block;
- adjust_pc(vcpu);
+ kvm_adjust_pc(vcpu);
local_irq_disable();
guest_enter_irqoff();
@@ -457,8 +449,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
kvm_sigset_deactivate(vcpu);
out:
- if (unlikely(vcpu_get_flag(vcpu, INCREMENT_PC)))
- adjust_pc(vcpu);
+ if (unlikely(vcpu_get_flag(vcpu, PENDING_EXCEPTION) ||
+ vcpu_get_flag(vcpu, INCREMENT_PC)))
+ kvm_adjust_pc(vcpu);
save_vx_regs(vcpu->arch.ctxt.vregs);
kernel_fpu_end(&fpu_save, KERNEL_FPC | KERNEL_VXR);
diff --git a/arch/s390/kvm/arm64/exception.c b/arch/s390/kvm/arm64/exception.c
new file mode 100644
index 000000000000..871e4e2c710a
--- /dev/null
+++ b/arch/s390/kvm/arm64/exception.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_emulate.h>
+#include <asm/sysreg-defs.h>
+
+#include <asm/pstate.h>
+
+/*
+ * This performs the exception entry at a given EL (@target_mode), stashing PC
+ * and PSTATE into ELR and SPSR respectively, and compute the new PC/PSTATE.
+ * The EL passed to this function *must* be a non-secure, privileged mode with
+ * bit 0 being set (PSTATE.SP == 1).
+ *
+ * When an exception is taken, most PSTATE fields are left unchanged in the
+ * handler. However, some are explicitly overridden (e.g. M[4:0]). Luckily all
+ * of the inherited bits have the same position in the AArch64/AArch32 SPSR_ELx
+ * layouts, so we don't need to shuffle these for exceptions from AArch32 EL0.
+ *
+ * For the SPSR_ELx layout for AArch64, see ARM DDI 0487E.a page C5-429.
+ * For the SPSR_ELx layout for AArch32, see ARM DDI 0487E.a page C5-426.
+ *
+ * Here we manipulate the fields in order of the AArch64 SPSR_ELx layout, from
+ * MSB to LSB.
+ */
+static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
+ enum exception_type type)
+{
+ unsigned long sctlr, vbar, old_pstate, new, mode;
+ u64 exc_offset;
+
+ old_pstate = *vcpu_cpsr(vcpu);
+ mode = old_pstate & (PSR_MODE_MASK | PSR_MODE32_BIT);
+
+ if (mode == target_mode)
+ exc_offset = CURRENT_EL_SP_ELx_VECTOR;
+ else if ((mode | PSR_MODE_THREAD_BIT) == target_mode)
+ exc_offset = CURRENT_EL_SP_EL0_VECTOR;
+ else if (!(mode & PSR_MODE32_BIT))
+ exc_offset = LOWER_EL_AArch64_VECTOR;
+ else
+ exc_offset = LOWER_EL_AArch32_VECTOR;
+
+ switch (target_mode) {
+ case PSR_MODE_EL1h:
+ vbar = vcpu_read_sys_reg(vcpu, VBAR_EL1);
+ sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
+ vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL1);
+ vcpu_write_sys_reg(vcpu, old_pstate, SPSR_EL1);
+ break;
+ default:
+ panic("Unknown PSR Mode: 0x%lx.", target_mode);
+ }
+
+ *vcpu_pc(vcpu) = vbar + exc_offset + type;
+
+ new = 0;
+
+ new |= (old_pstate & PSR_N_BIT);
+ new |= (old_pstate & PSR_Z_BIT);
+ new |= (old_pstate & PSR_C_BIT);
+ new |= (old_pstate & PSR_V_BIT);
+ new |= (old_pstate & PSR_DIT_BIT);
+ new |= (old_pstate & PSR_PAN_BIT);
+
+ if (!(sctlr & SCTLR_EL1_SPAN))
+ new |= PSR_PAN_BIT;
+
+ if (sctlr & SCTLR_ELx_DSSBS)
+ new |= PSR_SSBS_BIT;
+
+ new |= PSR_D_BIT;
+ new |= PSR_A_BIT;
+ new |= PSR_I_BIT;
+ new |= PSR_F_BIT;
+
+ new |= target_mode;
+
+ *vcpu_cpsr(vcpu) = new;
+}
+
+static void kvm_inject_exception(struct kvm_vcpu *vcpu)
+{
+ switch (vcpu_get_flag(vcpu, EXCEPT_MASK)) {
+ case unpack_vcpu_flag(EXCEPT_AA64_EL1_SYNC):
+ enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);
+ break;
+ }
+}
+
+/*
+ * Adjust the guest PC (and potentially exception state) depending on
+ * flags provided by the emulation code.
+ */
+void kvm_adjust_pc(struct kvm_vcpu *vcpu)
+{
+ if (vcpu_get_flag(vcpu, PENDING_EXCEPTION)) {
+ kvm_inject_exception(vcpu);
+ vcpu_clear_flag(vcpu, PENDING_EXCEPTION);
+ vcpu_clear_flag(vcpu, EXCEPT_MASK);
+ } else if (vcpu_get_flag(vcpu, INCREMENT_PC)) {
+ kvm_skip_instr(vcpu);
+ vcpu_clear_flag(vcpu, INCREMENT_PC);
+ }
+}
diff --git a/arch/s390/kvm/arm64/inject_fault.c b/arch/s390/kvm/arm64/inject_fault.c
index 650c041efde2..0216ffbd62ab 100644
--- a/arch/s390/kvm/arm64/inject_fault.c
+++ b/arch/s390/kvm/arm64/inject_fault.c
@@ -2,6 +2,42 @@
#include <asm/kvm_emulate.h>
+#define exception_esr_elx(__vcpu) ESR_EL1
+#define exception_far_elx(__vcpu) FAR_EL1
+
+static void pend_sync_exception(struct kvm_vcpu *vcpu)
+{
+ kvm_pend_exception(vcpu, EXCEPT_AA64_EL1_SYNC);
+}
+
+static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
+{
+ unsigned long cpsr = *vcpu_cpsr(vcpu);
+ bool is_aarch32 = vcpu_mode_is_32bit(vcpu);
+ u64 esr = 0;
+
+ if (kvm_vcpu_abt_iss1tw(vcpu))
+ esr |= ESR_ELx_FSC_SEA_TTW(kvm_vcpu_abt_gltl(vcpu));
+ else
+ esr |= ESR_ELx_FSC_EXTABT;
+
+ pend_sync_exception(vcpu);
+
+ if (kvm_vcpu_trap_il_is32bit(vcpu))
+ esr |= ESR_ELx_IL;
+
+ if (is_aarch32 || (cpsr & PSR_MODE_MASK) == PSR_MODE_EL0t)
+ esr |= (ESR_ELx_EC_IABT_LOW << ESR_ELx_EC_SHIFT);
+ else
+ esr |= (ESR_ELx_EC_IABT_CUR << ESR_ELx_EC_SHIFT);
+
+ if (!is_iabt)
+ esr |= ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT;
+
+ vcpu_write_sys_reg(vcpu, addr, ESR_EL1);
+ vcpu_write_sys_reg(vcpu, esr, FAR_EL1);
+}
+
/**
* kvm_inject_undefined - inject an undefined instruction into the guest
* @vcpu: The vCPU in which to inject the exception
@@ -11,11 +47,43 @@
*/
void kvm_inject_undefined(struct kvm_vcpu *vcpu)
{
- /* Stub until s390 supports arm64 sysregs TODO sysregs*/
+ u64 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);
+
+ pend_sync_exception(vcpu);
+
+ /*
+ * Build an unknown exception, depending on the instruction
+ * set.
+ */
+ if (kvm_vcpu_trap_il_is32bit(vcpu))
+ esr |= ESR_ELx_IL;
+
+ vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
+}
+
+static void __kvm_inject_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr)
+{
+ inject_abt64(vcpu, iabt, addr);
}
int kvm_inject_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr)
{
- /* Stub until s390 supports arm64 sysregs TODO sysregs*/
+ lockdep_assert_held(&vcpu->mutex);
+
+ __kvm_inject_sea(vcpu, iabt, addr);
return 1;
}
+
+void kvm_inject_size_fault(struct kvm_vcpu *vcpu)
+{
+ unsigned long addr, esr;
+
+ addr = kvm_vcpu_get_fault_ipa(vcpu);
+ addr |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(vcpu));
+
+ __kvm_inject_sea(vcpu, kvm_vcpu_trap_is_iabt(vcpu), addr);
+
+ esr = vcpu_read_sys_reg(vcpu, exception_esr_elx(vcpu));
+ esr &= ~GENMASK_ULL(5, 0);
+ vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
+}
--
2.53.0