linux-kernel - Re: [PATCH 04/24] arm: use asm-generic/mmu

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Message-Id: <1598450646.p1afhqiz8e.astroid@bobo.none>
Date:   Thu, 27 Aug 2020 00:14:52 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Russell King <linux@...linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        arcml <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH 04/24] arm: use asm-generic/mmu_context.h for no-op
 implementations

Excerpts from Vineet Gupta's message of July 28, 2020 2:14 pm:
> On 7/27/20 8:33 PM, Nicholas Piggin wrote:
>> Cc: Russell King <linux@...linux.org.uk>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Signed-off-by: Nicholas Piggin <npiggin@...il.com>
>> ---
>>  arch/arm/include/asm/mmu_context.h | 26 +++-----------------------
>>  1 file changed, 3 insertions(+), 23 deletions(-)
>> 
>> diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
>> index f99ed524fe41..84e58956fcab 100644
>> --- a/arch/arm/include/asm/mmu_context.h
>> +++ b/arch/arm/include/asm/mmu_context.h
>> @@ -26,6 +26,8 @@ void __check_vmalloc_seq(struct mm_struct *mm);
>>  #ifdef CONFIG_CPU_HAS_ASID
>>  
>>  void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk);
>> +
>> +#define init_new_context init_new_context
>>  static inline int
>>  init_new_context(struct task_struct *tsk, struct mm_struct *mm)
>>  {
>> @@ -92,32 +94,10 @@ static inline void finish_arch_post_lock_switch(void)
>>  
>>  #endif	/* CONFIG_MMU */
>>  
>> -static inline int
>> -init_new_context(struct task_struct *tsk, struct mm_struct *mm)
>> -{
>> -	return 0;
>> -}
>> -
>> -
>>  #endif	/* CONFIG_CPU_HAS_ASID */
>>  
>> -#define destroy_context(mm)		do { } while(0)
>>  #define activate_mm(prev,next)		switch_mm(prev, next, NULL)
> 
> Actually this can also go away too.
> 
> ARM switch_mm(prev, next, tsk) -> check_and_switch_context(next, tsk) but latter
> doesn't use @tsk at all. With patch below, you can remove above as well...

Thanks for reviewing. I did notice that might be possible but I was 
avoiding any change that wasn't completely trivial. It's a good point
to continue consolidating and simplifying though.

Thanks,
Nick

> 
> -------->
> From 672e0f78a94892794057a5a7542d85b71c1369c4 Mon Sep 17 00:00:00 2001
> From: Vineet Gupta <vgupta@...opsys.com>
> Date: Mon, 27 Jul 2020 21:12:42 -0700
> Subject: [PATCH] ARM: mm: check_and_switch_context() doesn't use @tsk arg
> 
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> ---
>  arch/arm/include/asm/efi.h         | 2 +-
>  arch/arm/include/asm/mmu_context.h | 5 ++---
>  arch/arm/mm/context.c              | 2 +-
>  3 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
> index 5dcf3c6011b7..0995b308149d 100644
> --- a/arch/arm/include/asm/efi.h
> +++ b/arch/arm/include/asm/efi.h
> @@ -37,7 +37,7 @@ int efi_set_mapping_permissions(struct mm_struct *mm,
> efi_memory_desc_t *md);
> 
>  static inline void efi_set_pgd(struct mm_struct *mm)
>  {
> -	check_and_switch_context(mm, NULL);
> +	check_and_switch_context(mm);
>  }
> 
>  void efi_virtmap_load(void);
> diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
> index f99ed524fe41..c96360fa3466 100644
> --- a/arch/arm/include/asm/mmu_context.h
> +++ b/arch/arm/include/asm/mmu_context.h
> @@ -25,7 +25,7 @@ void __check_vmalloc_seq(struct mm_struct *mm);
> 
>  #ifdef CONFIG_CPU_HAS_ASID
> 
> -void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk);
> +void check_and_switch_context(struct mm_struct *mm);
>  static inline int
>  init_new_context(struct task_struct *tsk, struct mm_struct *mm)
>  {
> @@ -47,8 +47,7 @@ static inline void a15_erratum_get_cpumask(int this_cpu, struct
> mm_struct *mm,
> 
>  #ifdef CONFIG_MMU
> 
> -static inline void check_and_switch_context(struct mm_struct *mm,
> -					    struct task_struct *tsk)
> +static inline void check_and_switch_context(struct mm_struct *mm)
>  {
>  	if (unlikely(mm->context.vmalloc_seq != init_mm.context.vmalloc_seq))
>  		__check_vmalloc_seq(mm);
> diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
> index b7525b433f3e..86c411e1d7cb 100644
> --- a/arch/arm/mm/context.c
> +++ b/arch/arm/mm/context.c
> @@ -234,7 +234,7 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
>  	return asid | generation;
>  }
> 
> -void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
> +void check_and_switch_context(struct mm_struct *mm)
>  {
>  	unsigned long flags;
>  	unsigned int cpu = smp_processor_id();
> -- 
> 2.20.1
> 
>