Hi Kirill, 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. > > On PAE we have to use cmpxchg8b as we cannot assume what is value of new pmd and > setting it up half-by-half can expose broken corrupted entry to CPU. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: H. Peter Anvin <hpa@xxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> I'll look at this from the arm64 perspective. It would be good if we can have a generic atomic implementation based on cmpxchg64 but I need to look at the details first. > +static inline pmd_t pmdp_establish(pmd_t *pmdp, pmd_t pmd) > +{ > + pmd_t old; > + > + /* > + * We cannot assume what is value of pmd here, so there's no easy way > + * to set if half by half. We have to fall back to cmpxchg64. > + */ > + { BTW, you are missing a "do" here (and it probably compiles just fine without it, though different behaviour). > + old = *pmdp; > + } while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd); > + > + return old; > +} -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>