[PATCH v6 09/14] KVM: s390: Dispatch to implementing function at top level of vm mem_op

Janis Schoetterl-Glausch
2023-01-25T21:26:38Z

Instead of having one function covering all mem_op operations,
have a function implementing absolute access and dispatch to that
function in its caller, based on the operation code.
This way additional future operations can be implemented by adding an
implementing function without changing existing operations.

Suggested-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
---
arch/s390/kvm/kvm-s390.c | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e0dfaa195949..588cf70dc81e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2791,7 +2791,7 @@ static void *mem_op_alloc_buf(struct kvm_s390_mem_op *mop)
return buf;
}

-static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
+static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
{
void __user *uaddr = (void __user *)mop->buf;
void *tmpbuf = NULL;
@@ -2802,17 +2802,6 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
if (r)
return r;

- /*
- * 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;
tmpbuf = mem_op_alloc_buf(mop);
if (IS_ERR(tmpbuf))
return PTR_ERR(tmpbuf);
@@ -2851,8 +2840,6 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
}
break;
}
- default:
- r = -EINVAL;
}

out_unlock:
@@ -2862,6 +2849,29 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
return r;
}

+static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
+{
+ /*
+ * 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;
+
+ switch (mop->op) {
+ case KVM_S390_MEMOP_ABSOLUTE_READ:
+ case KVM_S390_MEMOP_ABSOLUTE_WRITE:
+ return kvm_s390_vm_mem_op_abs(kvm, mop);
+ default:
+ return -EINVAL;
+ }
+}
+
long kvm_arch_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
--
2.34.1