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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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) >Signed-off-by: Lorenzo Stoakes (ARM) >--- 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 Tested-by: Lance Yang _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv