Re: [PATCH v4 05/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for arc, microblaze, xtensa

[Lance Yang <lance.yang@linux.dev>]

On Tue, Sep 22, 2026 at 04:35:36PM +0100, Lorenzo Stoakes (ARM) wrote:
>Each of these architectures directly free page tables without routing these
>changes through tlb_remove_ptdesc().
>
>The use of tlb_remove_ptdesc() is required for
>CONFIG_MMU_GATHER_RCU_TABLE_FREE to correctly free page tables under RCU,
>so simply update these architectures to use these functions.
>
>Since none of the architectures share page tables or do anything unusual,
>nothing complicated is required here.
>
>Therefore this is simply a mechanical change - convert __pud_free_tlb(),
>__pmd_free_tlb() and __pte_free_tlb() to use tlb_remove_ptdesc() as
>required.
>
>At the point this is in place, all mmu_gather page table freeing is
>performed under RCU, and thus MMU_GATHER_RCU_TABLE_FREE is selected for
>each architecture.
>
>Note that CONFIG_MMU_GATHER_RCU_TABLE_FREE is dependent on CONFIG_MMU for
>xtensa to reflect the fact that nommu does not implement page table
>gathering.
>
>This forms part of an overall effort to switch every architecture to this
>mode.
>
>Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
>Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
>---

Right, the old frees already end up in pagetable_dtor_free(). With
tlb_remove_ptdesc(), the same cleanup happens after an RCU grace period.

Makes sense to me, feel free to add:

Acked-by: Lance Yang <lance.yang@linux.dev>