KVM: s390: Storage key manipulation IOCTL

Add a new IOCTL to allow userspace to manipulate storage keys directly.

This will make it easier to write selftests related to storage keys.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Documentation/virt/kvm/api.rst

@@ -6517,6 +6517,40 @@ the capability to be present.
 
 `flags` must currently be zero.
 
+4.144 KVM_S390_KEYOP
+--------------------
+
+:Capability: KVM_CAP_S390_KEYOP
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_s390_keyop (in/out)
+:Returns: 0 in case of success, < 0 on error
+
+The specified key operation is performed on the given guest address. The
+previous storage key (or the relevant part thereof) will be returned in
+`key`.
+
+::
+
+  struct kvm_s390_keyop {
+	__u64 guest_addr;
+	__u8  key;
+	__u8  operation;
+  };
+
+Currently supported values for ``operation``:
+
+KVM_S390_KEYOP_ISKE
+  Returns the storage key for the guest address ``guest_addr`` in ``key``.
+
+KVM_S390_KEYOP_RRBE
+  Resets the reference bit for the guest address ``guest_addr``, returning the
+  R and C bits of the old storage key in ``key``; the remaining fields of
+  the storage key will be set to 0.
+
+KVM_S390_KEYOP_SSKE
+  Sets the storage key for the guest address ``guest_addr`` to the key
+  specified in ``key``, returning the previous value in ``key``.
 
 .. _kvm_run:
 
@@ -9287,6 +9321,14 @@ The presence of this capability indicates that KVM_RUN will update the
 KVM_RUN_X86_GUEST_MODE bit in kvm_run.flags to indicate whether the
 vCPU was executing nested guest code when it exited.
 
+8.46 KVM_CAP_S390_KEYOP
+-----------------------
+
+:Architectures: s390
+
+The presence of this capability indicates that the KVM_S390_KEYOP ioctl is
+available.
+
 KVM exits with the register state of either the L1 or L2 guest
 depending on which executed at the time of an exit. Userspace must
 take care to differentiate between these cases.

arch/s390/kvm/kvm-s390.c

@@ -554,6 +554,37 @@ static void __kvm_s390_exit(void)
 	debug_unregister(kvm_s390_dbf_uv);
 }
 
+static int kvm_s390_keyop(struct kvm_s390_mmu_cache *mc, struct kvm *kvm, int op,
+			  unsigned long addr, union skey skey)
+{
+	union asce asce = kvm->arch.gmap->asce;
+	gfn_t gfn = gpa_to_gfn(addr);
+	int r;
+
+	guard(read_lock)(&kvm->mmu_lock);
+
+	switch (op) {
+	case KVM_S390_KEYOP_SSKE:
+		r = dat_cond_set_storage_key(mc, asce, gfn, skey, &skey, 0, 0, 0);
+		if (r >= 0)
+			return skey.skey;
+		break;
+	case KVM_S390_KEYOP_ISKE:
+		r = dat_get_storage_key(asce, gfn, &skey);
+		if (!r)
+			return skey.skey;
+		break;
+	case KVM_S390_KEYOP_RRBE:
+		r = dat_reset_reference_bit(asce, gfn);
+		if (r > 0)
+			return r << 1;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return r;
+}
+
 /* Section: device related */
 long kvm_arch_dev_ioctl(struct file *filp,
 			unsigned int ioctl, unsigned long arg)
@@ -598,6 +629,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_DIAG318:
 	case KVM_CAP_IRQFD_RESAMPLE:
 	case KVM_CAP_S390_USER_OPEREXEC:
+	case KVM_CAP_S390_KEYOP:
 		r = 1;
 		break;
 	case KVM_CAP_SET_GUEST_DEBUG2:
@@ -2931,6 +2963,32 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 			r = -EFAULT;
 		break;
 	}
+	case KVM_S390_KEYOP: {
+		struct kvm_s390_mmu_cache *mc;
+		struct kvm_s390_keyop kop;
+		union skey skey;
+
+		if (copy_from_user(&kop, argp, sizeof(kop))) {
+			r = -EFAULT;
+			break;
+		}
+		skey.skey = kop.key;
+
+		mc = kvm_s390_new_mmu_cache();
+		if (!mc)
+			return -ENOMEM;
+
+		r = kvm_s390_keyop(mc, kvm, kop.operation, kop.guest_addr, skey);
+		kvm_s390_free_mmu_cache(mc);
+		if (r < 0)
+			break;
+
+		kop.key = r;
+		r = 0;
+		if (copy_to_user(argp, &kop, sizeof(kop)))
+			r = -EFAULT;
+		break;
+	}
 	case KVM_S390_ZPCI_OP: {
 		struct kvm_s390_zpci_op args;
 

include/uapi/linux/kvm.h

@@ -974,6 +974,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_GUEST_MEMFD_FLAGS 244
 #define KVM_CAP_ARM_SEA_TO_USER 245
 #define KVM_CAP_S390_USER_OPEREXEC 246
+#define KVM_CAP_S390_KEYOP 247
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
@@ -1219,6 +1220,15 @@ struct kvm_vfio_spapr_tce {
 	__s32	tablefd;
 };
 
+#define KVM_S390_KEYOP_ISKE 0x01
+#define KVM_S390_KEYOP_RRBE 0x02
+#define KVM_S390_KEYOP_SSKE 0x03
+struct kvm_s390_keyop {
+	__u64 guest_addr;
+	__u8  key;
+	__u8  operation;
+};
+
 /*
  * KVM_CREATE_VCPU receives as a parameter the vcpu slot, and returns
  * a vcpu fd.
@@ -1238,6 +1248,7 @@ struct kvm_vfio_spapr_tce {
 #define KVM_S390_UCAS_MAP        _IOW(KVMIO, 0x50, struct kvm_s390_ucas_mapping)
 #define KVM_S390_UCAS_UNMAP      _IOW(KVMIO, 0x51, struct kvm_s390_ucas_mapping)
 #define KVM_S390_VCPU_FAULT	 _IOW(KVMIO, 0x52, unsigned long)
+#define KVM_S390_KEYOP           _IOWR(KVMIO, 0x53, struct kvm_s390_keyop)
 
 /* Device model IOC */
 #define KVM_CREATE_IRQCHIP        _IO(KVMIO,   0x60)