[PATCH v2 0/3] KVM: s390: Enable AP instructions for pv-guests

[PATCH v2 0/3] KVM: s390: Enable AP instructions for pv-guests

[Steffen Eiden]

This series enables general KVM support for AP-passthrough for Secure
Execution guests (pv-guests).

To enable AP inside pv-guests two things have to be done/considered:
	1) set corresponding flags in the Create Secure Configuration UVC ifi
     firmware supports AP for pv-guests (patch 3).
	2) enable/disable AP in pv-guests if the VMM wants this (patch 2).

since v1:
  - PATCH 1: r-b from Claudio
  - PATCH 2: fixed formatting issues (Claudio)
  - PATCH 3: removed unnecessary checks (Claudio)

Steffen

Steffen Eiden (3):
  s390: uv: UV feature check utility
  KVM: s390: Add UV feature negotiation
  KVM: s390: pv:  Allow AP-instructions for pv guests

 arch/s390/include/asm/kvm_host.h |  2 ++
 arch/s390/include/asm/uv.h       | 17 ++++++++-
 arch/s390/include/uapi/asm/kvm.h | 25 +++++++++++++
 arch/s390/kernel/uv.c            |  2 +-
 arch/s390/kvm/kvm-s390.c         | 62 +++++++++++++++++++++++++++++++-
 arch/s390/kvm/pv.c               |  6 ++--
 arch/s390/mm/fault.c             |  2 +-
 7 files changed, 110 insertions(+), 6 deletions(-)

-- 
2.40.1

[PATCH v2 1/3] s390: uv: UV feature check utility

[Steffen Eiden]

Introduces a function to check the existence of an UV feature.
Refactor feature bit checks to use the new function.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
 arch/s390/include/asm/uv.h | 5 +++++
 arch/s390/kernel/uv.c      | 2 +-
 arch/s390/kvm/kvm-s390.c   | 2 +-
 arch/s390/mm/fault.c       | 2 +-
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index d6bb2f4f78d1..338845402324 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -397,6 +397,11 @@ struct uv_info {
 
 extern struct uv_info uv_info;
 
+static inline bool uv_has_feature(u8 feature_bit)
+{
+	return test_bit_inv(feature_bit, &uv_info.uv_feature_indications);
+}
+
 #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
 extern int prot_virt_guest;
 
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 66f0eb1c872b..152fd3e554c7 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -257,7 +257,7 @@ static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_str
 	 * shared page from a different protected VM will automatically also
 	 * transfer its ownership.
 	 */
-	if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications))
+	if (uv_has_feature(BIT_UV_FEAT_MISC))
 		return false;
 	if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
 		return false;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e6511608280c..813cc3d59c90 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2406,7 +2406,7 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
 	struct kvm_vcpu *vcpu;
 
 	/* Disable the GISA if the ultravisor does not support AIV. */
-	if (!test_bit_inv(BIT_UV_FEAT_AIV, &uv_info.uv_feature_indications))
+	if (!uv_has_feature(BIT_UV_FEAT_AIV))
 		kvm_s390_gisa_disable(kvm);
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index b5e1bea9194c..8a86dd725870 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -599,7 +599,7 @@ void do_secure_storage_access(struct pt_regs *regs)
 	 * reliable without the misc UV feature so we need to check
 	 * for that as well.
 	 */
-	if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) &&
+	if (uv_has_feature(BIT_UV_FEAT_MISC) &&
 	    !test_bit_inv(61, &regs->int_parm_long)) {
 		/*
 		 * When this happens, userspace did something that it
-- 
2.40.1

[PATCH v2 2/3] KVM: s390: Add UV feature negotiation

[Steffen Eiden]

Add a uv_feature list for pv-guests to the kvm cpu-model.
The feature bits 'AP-interpretation for secure guests' and
'AP-interrupt for secure guests' are available.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h |  2 ++
 arch/s390/include/uapi/asm/kvm.h | 25 +++++++++++++
 arch/s390/kvm/kvm-s390.c         | 60 ++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 2bbc3d54959d..7ae57ac352b2 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -817,6 +817,8 @@ struct kvm_s390_cpu_model {
 	__u64 *fac_list;
 	u64 cpuid;
 	unsigned short ibc;
+	/* subset of available uv features for pv-guests enabled by user space */
+	struct kvm_s390_vm_cpu_uv_feat uv_feat_guest;
 };
 
 typedef int (*crypto_hook)(struct kvm_vcpu *vcpu);
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index a73cf01a1606..b7f4bf5687c7 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -159,6 +159,31 @@ struct kvm_s390_vm_cpu_subfunc {
 	__u8 reserved[1728];
 };
 
+#define KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST	6
+#define KVM_S390_VM_CPU_MACHINE_UV_FEAT_GUEST	7
+
+#define KVM_S390_VM_CPU_UV_FEAT_NR_BITS	64
+struct kvm_s390_vm_cpu_uv_feat {
+	union {
+		struct {
+			__u64 res0 : 4;
+			__u64 ap : 1;		/* bit 4 */
+			__u64 ap_intr : 1;	/* bit 5 */
+			__u64 res6 : 58;
+		};
+		__u64 feat;
+	};
+};
+
+#define KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK  \
+	(((struct kvm_s390_vm_cpu_uv_feat){ \
+		  .ap = 1,                  \
+		  .ap_intr = 1,             \
+	  })                                \
+		 .feat)
+
+#define KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT ((struct kvm_s390_vm_cpu_uv_feat){})
+
 /* kvm attributes for crypto */
 #define KVM_S390_VM_CRYPTO_ENABLE_AES_KW	0
 #define KVM_S390_VM_CRYPTO_ENABLE_DEA_KW	1
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 813cc3d59c90..46d3108ad11f 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1531,6 +1531,29 @@ static int kvm_s390_set_processor_subfunc(struct kvm *kvm,
 	return 0;
 }
 
+static int kvm_s390_set_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_vm_cpu_uv_feat data = {};
+	unsigned long filter = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;
+
+	if (copy_from_user(&data, (void __user *)attr->addr, sizeof(data)))
+		return -EFAULT;
+	if (!bitmap_subset((unsigned long *)&data, &filter, KVM_S390_VM_CPU_UV_FEAT_NR_BITS))
+		return -EINVAL;
+
+	mutex_lock(&kvm->lock);
+	if (kvm->created_vcpus) {
+		mutex_unlock(&kvm->lock);
+		return -EBUSY;
+	}
+	kvm->arch.model.uv_feat_guest = data;
+	mutex_unlock(&kvm->lock);
+
+	VM_EVENT(kvm, 3, "SET: guest uv feat: 0x%16.16llx", data.feat);
+
+	return 0;
+}
+
 static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret = -ENXIO;
@@ -1545,6 +1568,9 @@ static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CPU_PROCESSOR_SUBFUNC:
 		ret = kvm_s390_set_processor_subfunc(kvm, attr);
 		break;
+	case KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST:
+		ret = kvm_s390_set_uv_feat(kvm, attr);
+		break;
 	}
 	return ret;
 }
@@ -1777,6 +1803,30 @@ static int kvm_s390_get_machine_subfunc(struct kvm *kvm,
 	return 0;
 }
 
+static int kvm_s390_get_processor_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_vm_cpu_uv_feat *src = &kvm->arch.model.uv_feat_guest;
+
+	if (copy_to_user((void __user *)attr->addr, src, sizeof(*src)))
+		return -EFAULT;
+	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16llx", kvm->arch.model.uv_feat_guest.feat);
+
+	return 0;
+}
+
+static int kvm_s390_get_machine_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_vm_cpu_uv_feat data = { .feat = uv_info.uv_feature_indications &
+							KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK };
+
+	BUILD_BUG_ON(sizeof(data) != sizeof(uv_info.uv_feature_indications));
+	if (copy_to_user((void __user *)attr->addr, &data, sizeof(struct kvm_s390_vm_cpu_uv_feat)))
+		return -EFAULT;
+	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16llx", data.feat);
+
+	return 0;
+}
+
 static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret = -ENXIO;
@@ -1800,6 +1850,12 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
 	case KVM_S390_VM_CPU_MACHINE_SUBFUNC:
 		ret = kvm_s390_get_machine_subfunc(kvm, attr);
 		break;
+	case KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST:
+		ret = kvm_s390_get_processor_uv_feat(kvm, attr);
+		break;
+	case KVM_S390_VM_CPU_MACHINE_UV_FEAT_GUEST:
+		ret = kvm_s390_get_machine_uv_feat(kvm, attr);
+		break;
 	}
 	return ret;
 }
@@ -1952,6 +2008,8 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 		case KVM_S390_VM_CPU_MACHINE_FEAT:
 		case KVM_S390_VM_CPU_MACHINE_SUBFUNC:
 		case KVM_S390_VM_CPU_PROCESSOR_SUBFUNC:
+		case KVM_S390_VM_CPU_MACHINE_UV_FEAT_GUEST:
+		case KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST:
 			ret = 0;
 			break;
 		default:
@@ -3296,6 +3354,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.model.cpuid = kvm_s390_get_initial_cpuid();
 	kvm->arch.model.ibc = sclp.ibc & 0x0fff;
 
+	kvm->arch.model.uv_feat_guest = KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT;
+
 	kvm_s390_crypto_init(kvm);
 
 	if (IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)) {
-- 
2.40.1

[PATCH v2 3/3] KVM: s390: pv: Allow AP-instructions for pv guests

[Steffen Eiden]

Introduces new feature bits and enablement flags for AP and AP IRQ
support.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
 arch/s390/include/asm/uv.h | 12 +++++++++++-
 arch/s390/kvm/pv.c         |  6 ++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 338845402324..913ccfaa9d76 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -99,6 +99,8 @@ enum uv_cmds_inst {
 enum uv_feat_ind {
 	BIT_UV_FEAT_MISC = 0,
 	BIT_UV_FEAT_AIV = 1,
+	BIT_UV_FEAT_AP = 4,
+	BIT_UV_FEAT_AP_INTR = 5,
 };
 
 struct uv_cb_header {
@@ -159,7 +161,15 @@ struct uv_cb_cgc {
 	u64 guest_handle;
 	u64 conf_base_stor_origin;
 	u64 conf_virt_stor_origin;
-	u64 reserved30;
+	u8  reserved30[6];
+	union {
+		struct {
+			u16 reserved : 14;
+			u16 ap_instr_intr : 1;
+			u16 ap_allow_instr : 1;
+		};
+		u16 raw;
+	} flags;
 	u64 guest_stor_origin;
 	u64 guest_stor_len;
 	u64 guest_sca;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index bf1fdc7bf89e..61d7712466c3 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -561,12 +561,14 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	uvcb.conf_base_stor_origin =
 		virt_to_phys((void *)kvm->arch.pv.stor_base);
 	uvcb.conf_virt_stor_origin = (u64)kvm->arch.pv.stor_var;
+	uvcb.flags.ap_allow_instr = kvm->arch.model.uv_feat_guest.ap;
+	uvcb.flags.ap_instr_intr = kvm->arch.model.uv_feat_guest.ap_intr;
 
 	cc = uv_call_sched(0, (u64)&uvcb);
 	*rc = uvcb.header.rc;
 	*rrc = uvcb.header.rrc;
-	KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x",
-		     uvcb.guest_handle, uvcb.guest_stor_len, *rc, *rrc);
+	KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x flags %04x",
+		     uvcb.guest_handle, uvcb.guest_stor_len, *rc, *rrc, uvcb.flags.raw);
 
 	/* Outputs */
 	kvm->arch.pv.handle = uvcb.guest_handle;
-- 
2.40.1

Re: [PATCH v2 2/3] KVM: s390: Add UV feature negotiation

[Heiko Carstens]

On Fri, Jul 28, 2023 at 11:23:40AM +0200, Steffen Eiden wrote:
> Add a uv_feature list for pv-guests to the kvm cpu-model.
> The feature bits 'AP-interpretation for secure guests' and
> 'AP-interrupt for secure guests' are available.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>  arch/s390/include/asm/kvm_host.h |  2 ++
>  arch/s390/include/uapi/asm/kvm.h | 25 +++++++++++++
>  arch/s390/kvm/kvm-s390.c         | 60 ++++++++++++++++++++++++++++++++
>  3 files changed, 87 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 2bbc3d54959d..7ae57ac352b2 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -817,6 +817,8 @@ struct kvm_s390_cpu_model {
>  	__u64 *fac_list;
>  	u64 cpuid;
>  	unsigned short ibc;
> +	/* subset of available uv features for pv-guests enabled by user space */
> +	struct kvm_s390_vm_cpu_uv_feat uv_feat_guest;
>  };
>  
>  typedef int (*crypto_hook)(struct kvm_vcpu *vcpu);
> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
> index a73cf01a1606..b7f4bf5687c7 100644
> --- a/arch/s390/include/uapi/asm/kvm.h
> +++ b/arch/s390/include/uapi/asm/kvm.h
> @@ -159,6 +159,31 @@ struct kvm_s390_vm_cpu_subfunc {
>  	__u8 reserved[1728];
>  };
>  
> +#define KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST	6
> +#define KVM_S390_VM_CPU_MACHINE_UV_FEAT_GUEST	7
> +
> +#define KVM_S390_VM_CPU_UV_FEAT_NR_BITS	64
> +struct kvm_s390_vm_cpu_uv_feat {
> +	union {
> +		struct {
> +			__u64 res0 : 4;
> +			__u64 ap : 1;		/* bit 4 */
> +			__u64 ap_intr : 1;	/* bit 5 */
> +			__u64 res6 : 58;

Using unnamed bitfields makes life easier.

> +#define KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK  \
> +	(((struct kvm_s390_vm_cpu_uv_feat){ \
> +		  .ap = 1,                  \
> +		  .ap_intr = 1,             \
> +	  })                                \
> +		 .feat)
> +
> +#define KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT ((struct kvm_s390_vm_cpu_uv_feat){})

Why are these two define uapi? Looks to me like both should be kernel
internal. Or why should user space know about them?

Also I think KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT is really odd
compared to all other code we have. Defining it to just 0 and assiging
to .feat instead of assigning a structure is the "usual way".

> +static int kvm_s390_set_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> +	struct kvm_s390_vm_cpu_uv_feat data = {};
> +	unsigned long filter = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;
> +
> +	if (copy_from_user(&data, (void __user *)attr->addr, sizeof(data)))
> +		return -EFAULT;
> +	if (!bitmap_subset((unsigned long *)&data, &filter, KVM_S390_VM_CPU_UV_FEAT_NR_BITS))
> +		return -EINVAL;

Casting a structure to an unsinged long pointer is also quite odd. I'd
would use get_user() & friends, and avoid all the casts. Patch below is
something I would do, also in order to reduce line lengths and breaks at
some places.. Feel free to ignore the whole patch, or take parts or all of
it (patch is on top of your complete series, and of course untested).

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index b7f4bf5687c7..c1b84c1a297d 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -166,23 +166,25 @@ struct kvm_s390_vm_cpu_subfunc {
 struct kvm_s390_vm_cpu_uv_feat {
 	union {
 		struct {
-			__u64 res0 : 4;
+			__u64 : 4;
 			__u64 ap : 1;		/* bit 4 */
 			__u64 ap_intr : 1;	/* bit 5 */
-			__u64 res6 : 58;
+			__u64 : 58;
 		};
 		__u64 feat;
 	};
 };
 
-#define KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK  \
-	(((struct kvm_s390_vm_cpu_uv_feat){ \
-		  .ap = 1,                  \
-		  .ap_intr = 1,             \
-	  })                                \
-		 .feat)
+#define KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK	\
+(						\
+	((struct kvm_s390_vm_cpu_uv_feat){	\
+		.ap = 1,			\
+		.ap_intr = 1,			\
+	})					\
+	.feat					\
+)
 
-#define KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT ((struct kvm_s390_vm_cpu_uv_feat){})
+#define KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT	0
 
 /* kvm attributes for crypto */
 #define KVM_S390_VM_CRYPTO_ENABLE_AES_KW	0
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index f383c48f965a..bbf4de3e27b3 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1533,12 +1533,13 @@ static int kvm_s390_set_processor_subfunc(struct kvm *kvm,
 
 static int kvm_s390_set_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
 {
-	struct kvm_s390_vm_cpu_uv_feat data = {};
-	unsigned long filter = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;
+	struct kvm_s390_vm_cpu_uv_feat __user *ptr = (void __user *)attr->addr;
+	unsigned long data, filter;
 
-	if (copy_from_user(&data, (void __user *)attr->addr, sizeof(data)))
+	filter = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;
+	if (get_user(data, &ptr->feat))
 		return -EFAULT;
-	if (!bitmap_subset((unsigned long *)&data, &filter, KVM_S390_VM_CPU_UV_FEAT_NR_BITS))
+	if (!bitmap_subset(&data, &filter, KVM_S390_VM_CPU_UV_FEAT_NR_BITS))
 		return -EINVAL;
 
 	mutex_lock(&kvm->lock);
@@ -1546,10 +1547,10 @@ static int kvm_s390_set_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
 		mutex_unlock(&kvm->lock);
 		return -EBUSY;
 	}
-	kvm->arch.model.uv_feat_guest = data;
+	kvm->arch.model.uv_feat_guest.feat = data;
 	mutex_unlock(&kvm->lock);
 
-	VM_EVENT(kvm, 3, "SET: guest uv feat: 0x%16.16llx", data.feat);
+	VM_EVENT(kvm, 3, "SET: guest uv feat: 0x%16.16lx", data);
 
 	return 0;
 }
@@ -1805,24 +1806,27 @@ static int kvm_s390_get_machine_subfunc(struct kvm *kvm,
 
 static int kvm_s390_get_processor_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
 {
-	struct kvm_s390_vm_cpu_uv_feat *src = &kvm->arch.model.uv_feat_guest;
+	struct kvm_s390_vm_cpu_uv_feat __user *dst = (void __user *)attr->addr;
+	unsigned long feat = kvm->arch.model.uv_feat_guest.feat;
 
-	if (copy_to_user((void __user *)attr->addr, src, sizeof(*src)))
+	if (put_user(feat, &dst->feat))
 		return -EFAULT;
-	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16llx", kvm->arch.model.uv_feat_guest.feat);
+	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16lx", feat);
 
 	return 0;
 }
 
 static int kvm_s390_get_machine_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
 {
-	struct kvm_s390_vm_cpu_uv_feat data = { .feat = uv_info.uv_feature_indications &
-							KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK };
+	struct kvm_s390_vm_cpu_uv_feat __user *dst = (void __user *)attr->addr;
+	unsigned long feat;
 
-	BUILD_BUG_ON(sizeof(data) != sizeof(uv_info.uv_feature_indications));
-	if (copy_to_user((void __user *)attr->addr, &data, sizeof(struct kvm_s390_vm_cpu_uv_feat)))
+	BUILD_BUG_ON(sizeof(*dst) != sizeof(uv_info.uv_feature_indications));
+
+	feat = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;
+	if (put_user(feat, &dst->feat))
 		return -EFAULT;
-	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16llx", data.feat);
+	VM_EVENT(kvm, 3, "GET: guest  uv feat: 0x%16.16lx", feat);
 
 	return 0;
 }
@@ -3354,7 +3358,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.model.cpuid = kvm_s390_get_initial_cpuid();
 	kvm->arch.model.ibc = sclp.ibc & 0x0fff;
 
-	kvm->arch.model.uv_feat_guest = KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT;
+	kvm->arch.model.uv_feat_guest.feat = KVM_S390_VM_CPU_UV_FEAT_GUEST_DEFAULT;
 
 	kvm_s390_crypto_init(kvm);