On Nov 10, 2022, at 7:17 AM, Peter Xu <peterx@xxxxxxxxxx> wrote: > +#ifdef CONFIG_DEBUG_VM > + /* > + * Having write bit for wr-protect-marked present ptes is fatal, > + * because it means the uffd-wp bit will be ignored and write will > + * just go through. > + * > + * Use any chance of pgtable walking to verify this (e.g., when > + * page swapped out or being migrated for all purposes). It means > + * something is already wrong. Tell the admin even before the > + * process crashes. We also nail it with wrong pgtable setup. > + */ > + WARN_ON_ONCE(wp && pte_write(pte)); How about VM_WARN_ON_ONCE() and no ifdef?
