diff --git a/linux-headers/asm-powerpc/kvm.h b/linux-headers/asm-powerpc/kvm.h
index fb3fddc..dea2156 100644
--- a/linux-headers/asm-powerpc/kvm.h
+++ b/linux-headers/asm-powerpc/kvm.h
@@ -327,6 +327,6 @@
 	__u32 reserved[8];
 };
 
-#define KVM_ONE_REG_PPC_HIOR	KVM_ONE_REG_PPC | 0x100
+#define KVM_REG_PPC_HIOR	(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x1)
 
 #endif /* __LINUX_KVM_POWERPC_H */
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index a8761d3..8c33a57 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -654,30 +654,33 @@
 
 /* Available with KVM_CAP_ONE_REG */
 
-#define KVM_ONE_REG_GENERIC		0x0000000000000000ULL
+#define KVM_REG_ARCH_MASK	0xff00000000000000ULL
+#define KVM_REG_GENERIC		0x0000000000000000ULL
 
 /*
  * Architecture specific registers are to be defined in arch headers and
  * ORed with the arch identifier.
  */
-#define KVM_ONE_REG_PPC			0x1000000000000000ULL
-#define KVM_ONE_REG_X86			0x2000000000000000ULL
-#define KVM_ONE_REG_IA64		0x3000000000000000ULL
-#define KVM_ONE_REG_ARM			0x4000000000000000ULL
-#define KVM_ONE_REG_S390		0x5000000000000000ULL
+#define KVM_REG_PPC		0x1000000000000000ULL
+#define KVM_REG_X86		0x2000000000000000ULL
+#define KVM_REG_IA64		0x3000000000000000ULL
+#define KVM_REG_ARM		0x4000000000000000ULL
+#define KVM_REG_S390		0x5000000000000000ULL
+
+#define KVM_REG_SIZE_SHIFT	52
+#define KVM_REG_SIZE_MASK	0x00f0000000000000ULL
+#define KVM_REG_SIZE_U8		0x0000000000000000ULL
+#define KVM_REG_SIZE_U16	0x0010000000000000ULL
+#define KVM_REG_SIZE_U32	0x0020000000000000ULL
+#define KVM_REG_SIZE_U64	0x0030000000000000ULL
+#define KVM_REG_SIZE_U128	0x0040000000000000ULL
+#define KVM_REG_SIZE_U256	0x0050000000000000ULL
+#define KVM_REG_SIZE_U512	0x0060000000000000ULL
+#define KVM_REG_SIZE_U1024	0x0070000000000000ULL
 
 struct kvm_one_reg {
 	__u64 id;
-	union {
-		__u8 reg8;
-		__u16 reg16;
-		__u32 reg32;
-		__u64 reg64;
-		__u8 reg128[16];
-		__u8 reg256[32];
-		__u8 reg512[64];
-		__u8 reg1024[128];
-	} u;
+	__u64 addr;
 };
 
 /*
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 0410901..f7c986c 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -740,6 +740,7 @@
     struct kvm_one_reg reg = {};
     struct kvm_sregs sregs = {};
     int ret;
+    uint64_t hior = env->spr[SPR_HIOR];
 
     cap.cap = KVM_CAP_PPC_PAPR;
     ret = kvm_vcpu_ioctl(env, KVM_ENABLE_CAP, &cap);
@@ -755,11 +756,14 @@
      *     Once we have qdev CPUs, move HIOR to a qdev property and
      *     remove this chunk.
      */
-    reg.id = KVM_ONE_REG_PPC_HIOR;
-    reg.u.reg64 = env->spr[SPR_HIOR];
+    reg.id = KVM_REG_PPC_HIOR;
+    reg.addr = (uintptr_t)&hior;
     ret = kvm_vcpu_ioctl(env, KVM_SET_ONE_REG, &reg);
-    if (ret) {
-        goto fail;
+    if (ret && 0) {
+        fprintf(stderr, "Couldn't set HIOR. Maybe you're running an old \n"
+                        "kernel with support for HV KVM but no PAPR PR \n"
+                        "KVM in which case things will work. If they don't \n"
+                        "please update your host kernel!\n");
     }
 
     /* Set SDR1 so kernel space finds the HTAB */