Re: [RFC PATCH v2 4/5] x86/amd_node: Add smn_set_roots() and smn_activate() for external SMN registration

[Lin Wang]

Hi Mario,

You're right. After a successful smn_set_roots(), smn_num_nodes is 
guaranteed to be non-zero because smn_set_roots() already rejects 
(!roots || !num_nodes). So checking !smn_roots here is sufficient.

Will fix in v3.

Thanks & Br,

Lin

On 4/24/2026 3:12 AM, Mario Limonciello wrote:
> > +/*
> > + * Activate the SMN access layer after roots have been registered via
> > + * smn_set_roots().  Creates the optional debugfs interface (gated by
> > + * the amd_smn_debugfs_enable boot parameter) and sets smn_exclusive so
> > + * that amd_smn_read()/amd_smn_write() begin accepting requests.
> > + *
> > + * @debugfs_name: directory name under arch_debugfs_dir (e.g. "amd_smn")
> > + *
> > + * Same serialization rules as smn_set_roots(): must be called exactly
> > + * once, at boot, after smn_set_roots() succeeds.
> > + */
> > +int smn_activate(const char *debugfs_name)
> > +{
> > +    if (!smn_roots || !smn_num_nodes)
> > +        return -EINVAL;
>
> You don't need the !smn_num_nodes check here.  smn_set_roots() already 
> has it.