On Fri, Nov 02, 2018 at 11:45:00AM +0530, Anshuman Khandual wrote: > On 10/17/2018 07:39 AM, Andrea Arcangeli wrote: > > What we need to do during split is an invalidate of the huge TLB. > > There's no pmd_trans_splitting anymore, so we only clear the present > > bit in the PTE despite pmd_present still returns true (just like > > PROT_NONE, nothing new in this respect). pmd_present never meant the > > On arm64, the problem is that pmd_present() is tied with pte_present() which > checks for PTE_VALID (also PTE_PROT_NONE) but which gets cleared during PTE > invalidation. pmd_present() returns false just after the first step of PMD > splitting. So pmd_present() needs to be decoupled from PTE_VALID which is > same as PMD_SECT_VALID and instead should depend upon a pte bit which sticks > around like PAGE_PSE as in case of x86. I am working towards a solution. Could we not just go via a PROT_NONE mapping during the split, instead of having to allocate a new software bit to treat these invalid ptes as present? Will
