1 files changed, 80 insertions, 0 deletions

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 7c672c7..8bb7318 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -39,6 +39,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 
 static bool cap_has_mp_state;
 static bool cap_has_inject_serror_esr;
+static bool cap_has_inject_ext_dabt;
 
 static ARMHostCPUFeatures arm_host_cpu_features;
 
@@ -245,6 +246,16 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         ret = -EINVAL;
     }
 
+    if (kvm_check_extension(s, KVM_CAP_ARM_NISV_TO_USER)) {
+        if (kvm_vm_enable_cap(s, KVM_CAP_ARM_NISV_TO_USER, 0)) {
+            error_report("Failed to enable KVM_CAP_ARM_NISV_TO_USER cap");
+        } else {
+            /* Set status for supporting the external dabt injection */
+            cap_has_inject_ext_dabt = kvm_check_extension(s,
+                                    KVM_CAP_ARM_INJECT_EXT_DABT);
+        }
+    }
+
     return ret;
 }
 
@@ -738,6 +749,29 @@ int kvm_get_vcpu_events(ARMCPU *cpu)
 
 void kvm_arch_pre_run(CPUState *cs, struct kvm_run *run)
 {
+    ARMCPU *cpu = ARM_CPU(cs);
+    CPUARMState *env = &cpu->env;
+
+    if (unlikely(env->ext_dabt_raised)) {
+        /*
+         * Verifying that the ext DABT has been properly injected,
+         * otherwise risking indefinitely re-running the faulting instruction
+         * Covering a very narrow case for kernels 5.5..5.5.4
+         * when injected abort was misconfigured to be
+         * an IMPLEMENTATION DEFINED exception (for 32-bit EL1)
+         */
+        if (!arm_feature(env, ARM_FEATURE_AARCH64) &&
+            unlikely(!kvm_arm_verify_ext_dabt_pending(cs))) {
+
+            error_report("Data abort exception with no valid ISS generated by "
+                   "guest memory access. KVM unable to emulate faulting "
+                   "instruction. Failed to inject an external data abort "
+                   "into the guest.");
+            abort();
+       }
+       /* Clear the status */
+       env->ext_dabt_raised = 0;
+    }
 }
 
 MemTxAttrs kvm_arch_post_run(CPUState *cs, struct kvm_run *run)
@@ -810,6 +844,47 @@ void kvm_arm_vm_state_change(void *opaque, int running, RunState state)
     }
 }
 
+/**
+ * kvm_arm_handle_dabt_nisv:
+ * @cs: CPUState
+ * @esr_iss: ISS encoding (limited) for the exception from Data Abort
+ *           ISV bit set to '0b0' -> no valid instruction syndrome
+ * @fault_ipa: faulting address for the synchronous data abort
+ *
+ * Returns: 0 if the exception has been handled, < 0 otherwise
+ */
+static int kvm_arm_handle_dabt_nisv(CPUState *cs, uint64_t esr_iss,
+                                    uint64_t fault_ipa)
+{
+    ARMCPU *cpu = ARM_CPU(cs);
+    CPUARMState *env = &cpu->env;
+    /*
+     * Request KVM to inject the external data abort into the guest
+     */
+    if (cap_has_inject_ext_dabt) {
+        struct kvm_vcpu_events events = { };
+        /*
+         * The external data abort event will be handled immediately by KVM
+         * using the address fault that triggered the exit on given VCPU.
+         * Requesting injection of the external data abort does not rely
+         * on any other VCPU state. Therefore, in this particular case, the VCPU
+         * synchronization can be exceptionally skipped.
+         */
+        events.exception.ext_dabt_pending = 1;
+        /* KVM_CAP_ARM_INJECT_EXT_DABT implies KVM_CAP_VCPU_EVENTS */
+        if (!kvm_vcpu_ioctl(cs, KVM_SET_VCPU_EVENTS, &events)) {
+            env->ext_dabt_raised = 1;
+            return 0;
+        }
+    } else {
+        error_report("Data abort exception triggered by guest memory access "
+                     "at physical address: 0x"  TARGET_FMT_lx,
+                     (target_ulong)fault_ipa);
+        error_printf("KVM unable to emulate faulting instruction.\n");
+    }
+    return -1;
+}
+
 int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
 {
     int ret = 0;
@@ -820,6 +895,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
             ret = EXCP_DEBUG;
         } /* otherwise return to guest */
         break;
+    case KVM_EXIT_ARM_NISV:
+        /* External DABT with no valid iss to decode */
+        ret = kvm_arm_handle_dabt_nisv(cs, run->arm_nisv.esr_iss,
+                                       run->arm_nisv.fault_ipa);
+        break;
     default:
         qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
                       __func__, run->exit_reason);