Re: [PATCH v7 09/14] KVM: s390: Dispatch to implementing function at top level of vm mem_op

Janosch Frank
2023-02-07T13:10:16Z

On 2/6/23 17:45, Janis Schoetterl-Glausch wrote:
> 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>
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Janosch Frank <frankja@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 0367c1a7e69a..707967a296f1 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2779,7 +2779,7 @@ static int mem_op_validate_common(struct kvm_s390_mem_op *mop, u64 supported_fla
> return 0;
> }
>
> -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;
> @@ -2790,17 +2790,6 @@ 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;
> if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
> tmpbuf = vmalloc(mop->size);
> if (!tmpbuf)
> @@ -2841,8 +2830,6 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
> }
> break;
> }
> - default:
> - r = -EINVAL;
> }
>
> out_unlock:
> @@ -2852,6 +2839,29 @@ 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)
> {