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

[Suren Baghdasaryan]

On Tue, Sep 1, 2026 at 4:06 AM Lorenzo Stoakes (ARM) <ljs at kernel.org> 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.
>
> This forms part of an overall effort to switch every architecture to this
> mode.
>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
> ---
>  arch/arc/Kconfig                      | 1 +
>  arch/arc/include/asm/pgalloc.h        | 6 +++---
>  arch/microblaze/Kconfig               | 1 +
>  arch/microblaze/include/asm/pgalloc.h | 2 +-
>  arch/xtensa/Kconfig                   | 1 +
>  arch/xtensa/include/asm/tlb.h         | 2 +-
>  6 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 2ed7186c81c5..7a7542b61823 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -47,6 +47,7 @@ config ARC
>         select HAVE_SYSCALL_TRACEPOINTS
>         select IRQ_DOMAIN
>         select LOCK_MM_AND_FIND_VMA
> +       select MMU_GATHER_RCU_TABLE_FREE
>         select MODULES_USE_ELF_RELA
>         select OF
>         select OF_EARLY_FLATTREE
> diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h
> index dfae070fe8d5..9b6c37f92e97 100644
> --- a/arch/arc/include/asm/pgalloc.h
> +++ b/arch/arc/include/asm/pgalloc.h
> @@ -72,7 +72,7 @@ static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
>         set_p4d(p4dp, __p4d((unsigned long)pudp));
>  }
>
> -#define __pud_free_tlb(tlb, pmd, addr)  pud_free((tlb)->mm, pmd)
> +#define __pud_free_tlb(tlb, pmd, addr)  tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))
>
>  #endif
>
> @@ -83,10 +83,10 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
>         set_pud(pudp, __pud((unsigned long)pmdp));
>  }
>
> -#define __pmd_free_tlb(tlb, pmd, addr)  pmd_free((tlb)->mm, pmd)
> +#define __pmd_free_tlb(tlb, pmd, addr)  tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))
>
>  #endif
>
> -#define __pte_free_tlb(tlb, pte, addr)  pte_free((tlb)->mm, pte)
> +#define __pte_free_tlb(tlb, pte, addr)  tlb_remove_ptdesc((tlb), page_ptdesc(pte))
>
>  #endif /* _ASM_ARC_PGALLOC_H */
> diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
> index 484ebb3baedf..af7e821e96c1 100644
> --- a/arch/microblaze/Kconfig
> +++ b/arch/microblaze/Kconfig
> @@ -41,6 +41,7 @@ config MICROBLAZE
>         select PCI_SYSCALL if PCI
>         select CPU_NO_EFFICIENT_FFS
>         select MMU_GATHER_NO_RANGE
> +       select MMU_GATHER_RCU_TABLE_FREE
>         select SPARSE_IRQ
>         select ZONE_DMA
>         select TRACE_IRQFLAGS_SUPPORT
> diff --git a/arch/microblaze/include/asm/pgalloc.h b/arch/microblaze/include/asm/pgalloc.h
> index 084a8a0dc239..ffee6a009219 100644
> --- a/arch/microblaze/include/asm/pgalloc.h
> +++ b/arch/microblaze/include/asm/pgalloc.h
> @@ -25,7 +25,7 @@ extern void __bad_pte(pmd_t *pmd);
>
>  extern pte_t *pte_alloc_one_kernel(struct mm_struct *mm);
>
> -#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, (pte))
> +#define __pte_free_tlb(tlb, pte, addr) tlb_remove_ptdesc((tlb), page_ptdesc(pte))
>
>  #define pmd_populate(mm, pmd, pte) \
>                         (pmd_val(*(pmd)) = (unsigned long)page_address(pte))
> diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
> index f2f9cd9cde50..33c4caee30e2 100644
> --- a/arch/xtensa/Kconfig
> +++ b/arch/xtensa/Kconfig
> @@ -55,6 +55,7 @@ config XTENSA
>         select HAVE_VIRT_CPU_ACCOUNTING_GEN
>         select IRQ_DOMAIN
>         select LOCK_MM_AND_FIND_VMA
> +       select MMU_GATHER_RCU_TABLE_FREE if MMU

And MMU is required because NOMMU does not perform mmu_gather
operations, same as in the previous patch? If so, maybe make a note of
it in the changelog?

>         select MODULES_USE_ELF_RELA
>         select PERF_USE_VMALLOC
>         select TRACE_IRQFLAGS_SUPPORT
> diff --git a/arch/xtensa/include/asm/tlb.h b/arch/xtensa/include/asm/tlb.h
> index 8c3ceb427018..6fb7b78154f6 100644
> --- a/arch/xtensa/include/asm/tlb.h
> +++ b/arch/xtensa/include/asm/tlb.h
> @@ -16,7 +16,7 @@
>
>  #include <asm-generic/tlb.h>
>
> -#define __pte_free_tlb(tlb, pte, address)      pte_free((tlb)->mm, pte)
> +#define __pte_free_tlb(tlb, pte, address)      tlb_remove_ptdesc((tlb), page_ptdesc(pte))
>
>  void check_tlb_sanity(void);
>
>
> --
> 2.55.0
>