Re: [PATCH v2 01/23] asm-generic: add generic MMU versions of mmu context functions

Mike Rapoport
2020-09-01T06:49:51Z

On Thu, Aug 27, 2020 at 12:52:27AM +1000, Nicholas Piggin wrote:
> Many of these are no-ops on many architectures, so extend mmu_context.h
> to cover MMU and NOMMU, and split the NOMMU bits out to nommu_context.h
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linux-arch@vger.kernel.org
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> arch/microblaze/include/asm/mmu_context.h | 2 +-
> arch/sh/include/asm/mmu_context.h | 2 +-
> include/asm-generic/mmu_context.h | 57 +++++++++++++++++------
> include/asm-generic/nommu_context.h | 19 ++++++++
> 4 files changed, 64 insertions(+), 16 deletions(-)
> create mode 100644 include/asm-generic/nommu_context.h
>
> diff --git a/arch/microblaze/include/asm/mmu_context.h b/arch/microblaze/include/asm/mmu_context.h
> index f74f9da07fdc..34004efb3def 100644
> --- a/arch/microblaze/include/asm/mmu_context.h
> +++ b/arch/microblaze/include/asm/mmu_context.h
> @@ -2,5 +2,5 @@
> #ifdef CONFIG_MMU
> # include <asm/mmu_context_mm.h>
> #else
> -# include <asm-generic/mmu_context.h>
> +# include <asm-generic/nommu_context.h>
> #endif
> diff --git a/arch/sh/include/asm/mmu_context.h b/arch/sh/include/asm/mmu_context.h
> index f664e51e8a15..461b1304580b 100644
> --- a/arch/sh/include/asm/mmu_context.h
> +++ b/arch/sh/include/asm/mmu_context.h
> @@ -133,7 +133,7 @@ static inline void switch_mm(struct mm_struct *prev,
> #define set_TTB(pgd) do { } while (0)
> #define get_TTB() (0)
>
> -#include <asm-generic/mmu_context.h>
> +#include <asm-generic/nommu_context.h>
>
> #endif /* CONFIG_MMU */
>
> diff --git a/include/asm-generic/mmu_context.h b/include/asm-generic/mmu_context.h
> index 6be9106fb6fb..86cea80a50df 100644
> --- a/include/asm-generic/mmu_context.h
> +++ b/include/asm-generic/mmu_context.h
> @@ -3,44 +3,73 @@
> #define __ASM_GENERIC_MMU_CONTEXT_H
>
> /*
> - * Generic hooks for NOMMU architectures, which do not need to do
> - * anything special here.
> + * Generic hooks to implement no-op functionality.
> */
>
> -#include <asm-generic/mm_hooks.h>
> -
> struct task_struct;
> struct mm_struct;
>
> +/*
> + * enter_lazy_tlb - Called when "tsk" is about to enter lazy TLB mode.
> + *
> + * @mm: the currently active mm context which is becoming lazy
> + * @tsk: task which is entering lazy tlb
> + *
> + * tsk->mm will be NULL
> + */
> +#ifndef enter_lazy_tlb
> static inline void enter_lazy_tlb(struct mm_struct *mm,
> struct task_struct *tsk)
> {
> }
> +#endif
>
> +/**
> + * init_new_context - Initialize context of a new mm_struct.
> + * @tsk: task struct for the mm
> + * @mm: the new mm struct

'make *docs' will complain here about missing Return: description

> + */
> +#ifndef init_new_context
> static inline int init_new_context(struct task_struct *tsk,
> struct mm_struct *mm)
> {
> return 0;
> }
> +#endif

Most architectures have non-trivial init_new_context, maybe this
should go into nommu_context.h?

> +/**
> + * destroy_context - Undo init_new_context when the mm is going away
> + * @mm: old mm struct
> + */
> +#ifndef destroy_context
> static inline void destroy_context(struct mm_struct *mm)
> {
> }
> +#endif
>
> -static inline void deactivate_mm(struct task_struct *task,
> - struct mm_struct *mm)
> -{
> -}
> -
> -static inline void switch_mm(struct mm_struct *prev,
> - struct mm_struct *next,
> - struct task_struct *tsk)
> +/**
> + * activate_mm - called after exec switches the current task to a new mm, to switch to it
> + * @prev_mm: previous mm of this task
> + * @next_mm: new mm
> + */
> +#ifndef activate_mm
> +static inline void activate_mm(struct mm_struct *prev_mm,
> + struct mm_struct *next_mm)
> {
> + switch_mm(prev_mm, next_mm, current);
> }
> +#endif
>
> -static inline void activate_mm(struct mm_struct *prev_mm,
> - struct mm_struct *next_mm)
> +/**
> + * dectivate_mm - called when an mm is released after exit or exec switches away from it
> + * @tsk: the task
> + * @mm: the old mm
> + */
> +#ifndef deactivate_mm
> +static inline void deactivate_mm(struct task_struct *tsk,
> + struct mm_struct *mm)
> {
> }
> +#endif
>
> #endif /* __ASM_GENERIC_MMU_CONTEXT_H */
> diff --git a/include/asm-generic/nommu_context.h b/include/asm-generic/nommu_context.h
> new file mode 100644
> index 000000000000..4f916f9e16cd
> --- /dev/null
> +++ b/include/asm-generic/nommu_context.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_GENERIC_NOMMU_H
> +#define __ASM_GENERIC_NOMMU_H
> +
> +/*
> + * Generic hooks for NOMMU architectures, which do not need to do
> + * anything special here.
> + */
> +#include <asm-generic/mm_hooks.h>
> +
> +static inline void switch_mm(struct mm_struct *prev,
> + struct mm_struct *next,
> + struct task_struct *tsk)
> +{
> +}
> +
> +#include <asm-generic/mmu_context.h>
> +
> +#endif /* __ASM_GENERIC_NOMMU_H */
> --
> 2.23.0
>
>

--
Sincerely yours,
Mike.