On 17/03/2025 14:16, Kevin Brodsky wrote:
The complications in those special pgtable allocators beg the question: does it really make sense to treat efi_mm and init_mm differently in e.g. apply_to_pte_range()? Maybe what we really need is a way to tell if an mm corresponds to user memory or not, and never use split locks for non-user mm's. Feedback and suggestions welcome!
The difference in treatment is whether or not the ptl is taken, right? So the real question is when calling apply_to_pte_range() for efi_mm, is there already a higher level serialization mechanism that prevents racy accesses? For init_mm, I think this is handled implicitly because there is no way for user space to cause apply_to_pte_range() for an arbitrary piece of kernel memory. Although I can't even see where apply_to_page_range() is called for efi_mm. FWIW, contpte.c has mm_is_user() which is used by arm64. Thanks, Ryan
