Michael Ellerman <m...@ellerman.id.au> writes: > Ram Pai <linux...@us.ibm.com> writes: > >> Handle Data and Instruction exceptions caused by memory >> protection-key. >> >> The CPU will detect the key fault if the HPTE is already >> programmed with the key. >> >> However if the HPTE is not hashed, a key fault will not >> be detected by the hardware. The software will detect >> pkey violation in such a case. > > That seems like the wrong trade off to me. > > It means every fault has to go through arch_vma_access_permitted(), > which is at least a function call in the best case, even when pkeys are > not in use, and/or the range in question is not protected by a key.
We don't really need to call arch_vma_access_permitted() in arch/powerpc/ do_page_fault(). Core kernel does that in handle_mm_fault(). So if the first fault is a bad access handle_mm_fault handle this. If it is a valid access we insert the right hash page table entry and then we do a wrong access, we detect that a key fault in the low level hash fault handler. IIUC, the call the arch_vma_access_permitted() from arch/powerpc/ can go away? -aneesh
