Issuing a memop on a protected vm does not make sense, neither is the memory readable/writable, nor does it make sense to check storage keys. This is why the ioctl will return -EINVAL when it detects the vm to be protected. However, in order to ensure that the vm cannot become protected during the memop, the kvm->lock would need to be taken for the duration of the ioctl. This is also required because kvm_s390_pv_is_protected asserts that the lock must be held. Instead, don't try to prevent this. If user space enables secure execution concurrently with a memop it must accecpt the possibility of the memop failing. Still check if the vm is currently protected, but without locking and consider it a heuristic. Fixes: ef11c9463ae0 ("KVM: s390: Add vm IOCTL for key checked guest absolute memory access") Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> --- arch/s390/kvm/kvm-s390.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index ca96f84db2cc..53adbe86a68f 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2385,7 +2385,16 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) return -EINVAL; if (mop->size > MEM_OP_MAX_SIZE) return -E2BIG; - if (kvm_s390_pv_is_protected(kvm)) + /* + * This is technically a heuristic only, if the kvm->lock is not + * taken, it is not guaranteed that the vm is/remains non-protected. + * This is ok from a kernel perspective, wrongdoing is detected + * on the access, -EFAULT is returned and the vm may crash the + * next time it accesses the memory in question. + * There is no sane usecase to do switching and a memop on two + * different CPUs at the same time. + */ + if (kvm_s390_pv_get_handle(kvm)) return -EINVAL; if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) { if (access_key_invalid(mop->key)) base-commit: c9b8fecddb5bb4b67e351bbaeaa648a6f7456912 -- 2.32.0