On Mon, Jan 23, 2023 at 12:07:05PM +0100, David Hildenbrand wrote: > > > commit bedf03416913d88c796288f9dca109a53608c745 > > > Author: Yang Shi <shy828301@xxxxxxxxx> > > > Date: Wed Sep 7 11:01:44 2022 -0700 > > > > > > powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush > > > The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will > > > move to use RCU instead of disabling local interrupts in fast-GUP. Using > > > an IPI is the old-styled way of serializing against fast-GUP although it > > > still works as expected now. > > > And fast-GUP now fixed the potential race with THP collapse by checking > > > whether PMD is changed or not. So IPI broadcast in radix pmd collapse > > > flush is not necessary anymore. But it is still needed for hash TLB. > > > > Okay. But I think tlb_remove_table_sync_one() belongs inside > > pmdp_collapse_flush(). Collapsing pmd table into huge page without > > serialization is a bug. They should not be separate. > > Agreed. But I wonder if it should be moved into a generic > pmdp_collapse_flush(), that calls an arch specific __pmdp_collapse_flush(). Um? There's no __pmdp_collapse_flush(). Architectural code overrides pmdp_collapse_flush() altogether. It has know how to serialize properly for the arch. -- Kiryl Shutsemau / Kirill A. Shutemov
