[PATCH v2 7/7] mm: update lazy_mmu documentation

[Yeoreum Yun]

Reviewed-by: Yeoreum Yun <yeoreum.yun at arm.com>

On Mon, Sep 08, 2025 at 08:39:31AM +0100, Kevin Brodsky wrote:
> We now support nested lazy_mmu sections on all architectures
> implementing the API. Update the API comment accordingly.
>
> Acked-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
> Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
> ---
>  include/linux/pgtable.h | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index df0eb898b3fc..85cd1fdb914f 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -228,8 +228,18 @@ static inline int pmd_dirty(pmd_t pmd)
>   * of the lazy mode. So the implementation must assume preemption may be enabled
>   * and cpu migration is possible; it must take steps to be robust against this.
>   * (In practice, for user PTE updates, the appropriate page table lock(s) are
> - * held, but for kernel PTE updates, no lock is held). Nesting is not permitted
> - * and the mode cannot be used in interrupt context.
> + * held, but for kernel PTE updates, no lock is held). The mode cannot be used
> + * in interrupt context.
> + *
> + * Calls may be nested: an arch_{enter,leave}_lazy_mmu_mode() pair may be called
> + * while the lazy MMU mode has already been enabled. An implementation should
> + * handle this using the state returned by enter() and taken by the matching
> + * leave() call; the LAZY_MMU_{DEFAULT,NESTED} flags can be used to indicate
> + * whether this enter/leave pair is nested inside another or not. (It is up to
> + * the implementation to track whether the lazy MMU mode is enabled at any point
> + * in time.) The expectation is that leave() will flush any batched state
> + * unconditionally, but only leave the lazy MMU mode if the passed state is not
> + * LAZY_MMU_NESTED.
>   */
>  #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
>  typedef int lazy_mmu_state_t;
> --
> 2.47.0
>
>

--
Sincerely,
Yeoreum Yun