Re: [PATCH v4 3/4] KVM: s390: Add UV feature negotiation

Michael Mueller <mimu@xxxxxxxxxxxxx> · Thu, 17 Aug 2023 13:49:06 +0200

On 15.08.23 17:14, 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@xxxxxxxxxxxxx>
Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>

Reviewed-by: Michael Mueller <mimu@xxxxxxxxxxxxx>

but a minor comment, see below.

---
  arch/s390/include/asm/kvm_host.h |  2 +
  arch/s390/include/uapi/asm/kvm.h | 16 +++++++
  arch/s390/kvm/kvm-s390.c         | 73 ++++++++++++++++++++++++++++++++
  3 files changed, 91 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 91bfecb91321..427f9528a7b6 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..abe926d43cbe 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -159,6 +159,22 @@ 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 : 4;
+			__u64 ap : 1;		/* bit 4 */
+			__u64 ap_intr : 1;	/* bit 5 */
+			__u64 : 58;
+		};
+		__u64 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..b3f17e014cab 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1531,6 +1531,39 @@ static int kvm_s390_set_processor_subfunc(struct kvm *kvm,
  	return 0;
  }

+#define KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK	\
+(						\
+	((struct kvm_s390_vm_cpu_uv_feat){	\
+		.ap = 1,			\
+		.ap_intr = 1,			\
+	})					\
+	.feat					\
+)
+
+static int kvm_s390_set_uv_feat(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_vm_cpu_uv_feat __user *ptr = (void __user *)attr->addr;
+	unsigned long data, filter;
+
+	filter = uv_info.uv_feature_indications & KVM_S390_VM_CPU_UV_FEAT_GUEST_MASK;

if get_user() fails the uv feature bits in "filter" are
calculated in vain

+	if (get_user(data, &ptr->feat))
+		return -EFAULT;

could be done here, but that's really minor to me

+	if (!bitmap_subset(&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.feat = data;
+	mutex_unlock(&kvm->lock);
+
+	VM_EVENT(kvm, 3, "SET: guest UV-feat: 0x%16.16lx", data);
+
+	return 0;
+}
+
  static int kvm_s390_set_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
  {
  	int ret = -ENXIO;
@@ -1545,6 +1578,9 @@ 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 +1813,33 @@ 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 __user *dst = (void __user *)attr->addr;
+	unsigned long feat = kvm->arch.model.uv_feat_guest.feat;
+
+	if (put_user(feat, &dst->feat))
+		return -EFAULT;
+	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 __user *dst = (void __user *)attr->addr;
+	unsigned long 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%16.16lx", feat);
+
+	return 0;
+}
+
  static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
  {
  	int ret = -ENXIO;
@@ -1800,6 +1863,12 @@ 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 +2021,8 @@ 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 +3367,8 @@ 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.feat = 0;
+
  	kvm_s390_crypto_init(kvm);

  	if (IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)) {






