On 19.11.23 17:57, Alexandru Elisei wrote:
To enable tagging on a memory range, userspace can use mprotect() with the
PROT_MTE access flag. Pages already mapped in the VMA don't have the
associated tag storage block reserved, so mark the PTEs as
PAGE_FAULT_ON_ACCESS to trigger a fault next time they are accessed, and
reserve the tag storage on the fault path.
That sounds alot like fake PROT_NONE. Would there be a way to unify hat
handling and simply reuse pte_protnone()? For example, could we special
case on VMA flags?
Like, don't do NUMA hinting in these special VMAs. Then, have something
like:
if (pte_protnone(vmf->orig_pte))
return handle_pte_protnone(vmf);
In there, special case on the VMA flags.
I *suspect* that handle_page_missing_tag_storage() stole (sorry :P) some
code from the prot_none handling path. At least the recovery path and
writability handling looks like it better be located shared in
handle_pte_protnone() as well.
That might take some magic out of this patch.
--
Cheers,
David / dhildenb
