On Wed, Sep 23, 2026 at 09:16:34PM +0800, Lance Yang wrote: > > On Tue, Sep 22, 2026 at 04:35:40PM +0100, Lorenzo Stoakes (ARM) wrote: > >sun3 and coldfire are already supported, however motorola requires a little > >more care. > > > >Here, custom table removal logic is required, so > >CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE is enabled for m68k-motorola. > > > >Firstly as part of this change, the page table level must be communicated > >to the underlying __tlb_remove_table() implementation. > > > >Take advantage of the fact that page tables are aligned by more than enough > >to permit setting TABLE_PTE or TABLE_PMD in the low bits of the pointer, > >and store this there. > > > >Then update __pte_free_tlb() and __pmd_free_tlb() to pass this through, > >then have __tlb_remove_table() decode this and pass it to > >free_pointer_table(). > > > >The page table freeing is performed via call_rcu(), so free_pointer_table() > >now will be invoked from softirq context, and as such may be re-entrant. > > > >Introduce an irq save/restore spinlock to handle this, and hold it over the > >time a given ptable entry is being referenced in both get_pointer_table() > >and free_pointer_table(). > > > >In order to make things a little easier in this respect, separate out the > >logic for adding a new ptable entry into add_pointer_table() and only hold > >the lock during ptable entry insertion in this case. > > > >Note that original list_add_tail(new, dp) added new prior to dp, which is > >ptable_list[type].next, i.e. after ptable_list[type]. > > > >The equivalent therefore is list_add(new, &ptable_list[type]), which adds > >new after ptable_list[type], only without needing to make reference to dp. > > > >Note that, as m68k-motorola specifies CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE, it > >does not enable CONFIG_PT_RECLAIM. This isn't meaningfully impactful. > > > >With this applied, all of m68k implements CONFIG_MMU_GATHER_RCU_TABLE_FREE. > > > >This forms part of an overall effort to switch every architecture to this > >mode. > > > >Acked-by: Kiryl Shutsemau (Meta) <[email protected]> > >Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> > >--- > > I wondered about slot reuse during the RCU wait, but that can't happen :) > > The slot stays marked busy until free_pointer_table() runs after RCU, and > the last free unlinks the page under ptable_lock. > > Also ran page-table teardown stress and fork/exec churn on > qemu-system-m68k (virt, m68040, CONFIG_MMU_MOTOROLA=y). All 40 rounds ran > cleanly :D > > Acked-by: Lance Yang <[email protected]> > > Tested-by: Lance Yang <[email protected]>
Great, thanks! Really appreciate the testing :) -- Cheers, Lorenzo
