[PATCH v6 28/28] KVM: s390: Storage key manipulation IOCTL

Claudio Imbrenda
2025-12-22T16:51:19Z

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

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

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
arch/s390/kvm/kvm-s390.c | 57 ++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 10 +++++++
2 files changed, 67 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 47f2794af2fb..7f28b556b460 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/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)
@@ -2931,6 +2962,32 @@ 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.user_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;

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index dddb781b0507..845417e56778 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1219,6 +1219,15 @@ struct kvm_vfio_spapr_tce {
__s32 tablefd;
};

+#define KVM_S390_KEYOP_SSKE 0x01
+#define KVM_S390_KEYOP_ISKE 0x02
+#define KVM_S390_KEYOP_RRBE 0x03
+struct kvm_s390_keyop {
+ __u64 user_addr;
+ __u8 key;
+ __u8 operation;
+};
+
/*
* KVM_CREATE_VCPU receives as a parameter the vcpu slot, and returns
* a vcpu fd.
@@ -1238,6 +1247,7 @@ 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)
--
2.52.0