Messages in this thread | | | Subject | Re: [PATCHv2 1/3] x86/mm: Provide pmdp_establish() helper | From | Vineet Gupta <> | Date | Wed, 21 Jun 2017 10:20:47 -0700 |
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On 06/21/2017 10:16 AM, Kirill A. Shutemov wrote: > On Wed, Jun 21, 2017 at 08:49:03AM -0700, Vineet Gupta wrote: >> On 06/21/2017 04:27 AM, Catalin Marinas wrote: >>> On Wed, Jun 21, 2017 at 12:53:03PM +0300, Kirill A. Shutemov wrote: >>>>>>>>> On Thu, Jun 15, 2017 at 05:52:22PM +0300, Kirill A. Shutemov wrote: >>>>>>>>>> We need an atomic way to setup pmd page table entry, avoiding races with >>>>>>>>>> CPU setting dirty/accessed bits. This is required to implement >>>>>>>>>> pmdp_invalidate() that doesn't loose these bits. >>> [...] >>>> Any chance you could help me with arm too? >>> On arm (ARMv7 with LPAE) we don't have hardware updates of the >>> access/dirty bits, so a generic implementation would suffice. I didn't >>> find one in your patches, so here's an untested version: >>> >>> static inline pmd_t pmdp_establish(struct mm_struct *mm, unsigned long address, >>> pmd_t *pmdp, pmd_t pmd) >>> { >>> pmd_t old_pmd = *pmdp; >>> set_pmd_at(mm, address, pmdp, pmd); >>> return old_pmd; >>> } >> So it seems the discussions have settled down and pmdp_establish() can be >> implemented in generic way as above and it will suffice if arch doesn't have >> a special need. It would be nice to add the comment above generic version >> that it only needs to be implemented if hardware sets the accessed/dirty >> bits ! >> >> Then nothing special is needed for ARC - right ? > I will define generic version as Catalin proposed with a comment, but > under the name generic_pmdp_establish. An arch can make use of it by > > #define pmdp_establish generic_pmdp_establish
Can you do that for ARC in your next posting - or want me to once you have posted that ?
> I don't want it to be used by default without attention from architecture > maintainer. It can lead unnoticied breakage if THP got enabled on new > arch.
Makes sense !
-Vineet
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