linux-kernel - Re: [PATCH -next] powerpc/book3s64: fix link error with CONFIG_PPC_RADIX

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Message-ID: <39a976b8-896c-e878-bac7-50bbf3ccbc4f@csgroup.eu>
Date:   Sun, 6 Sep 2020 08:50:18 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Yang Yingliang <yangyingliang@...wei.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] powerpc/book3s64: fix link error with
 CONFIG_PPC_RADIX_MMU=n



Le 05/09/2020 à 13:25, Yang Yingliang a écrit :
> Fix link error when CONFIG_PPC_RADIX_MMU is disabled:
> powerpc64-linux-gnu-ld: arch/powerpc/platforms/pseries/lpar.o:(.toc+0x0): undefined reference to `mmu_pid_bits'
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> ---
>   arch/powerpc/mm/book3s64/mmu_context.c | 4 ++++

In your commit log, you are just mentionning 
arch/powerpc/platforms/pseries/lpar.o, which is right.

You shouldn't need to modify arch/powerpc/mm/book3s64/mmu_context.c at 
all, see below.

>   arch/powerpc/platforms/pseries/lpar.c  | 2 ++
>   2 files changed, 6 insertions(+)
> 
> diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c
> index 0ba30b8b935b..a8e292cd88f0 100644
> --- a/arch/powerpc/mm/book3s64/mmu_context.c
> +++ b/arch/powerpc/mm/book3s64/mmu_context.c
> @@ -152,6 +152,7 @@ void hash__setup_new_exec(void)
>   
>   static int radix__init_new_context(struct mm_struct *mm)
>   {
> +#ifdef CONFIG_PPC_RADIX_MMU

This shouldn't be required. radix__init_new_context() is only called 
when radix_enabled() returns true.
As it is a static function, when it is not called it gets optimised 
away, so you will never get an undefined reference to `mmu_pid_bits` there.

>   	unsigned long rts_field;
>   	int index, max_id;
>   
> @@ -177,6 +178,9 @@ static int radix__init_new_context(struct mm_struct *mm)
>   	mm->context.hash_context = NULL;
>   
>   	return index;
> +#else
> +	return -ENOTSUPP;
> +#endif
>   }
>   
>   int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
> index baf24eacd268..e454e218dbba 100644
> --- a/arch/powerpc/platforms/pseries/lpar.c
> +++ b/arch/powerpc/platforms/pseries/lpar.c
> @@ -1726,10 +1726,12 @@ void __init hpte_init_pseries(void)
>   
>   void radix_init_pseries(void)
>   {
> +#ifdef CONFIG_PPC_RADIX_MMU

This function is only called from 
/arch/powerpc/mm/book3s64/radix_pgtable.c which is only built when 
CONFIG_PPC_RADIX_MMU is selected.

So the entire function should be encloded in the #ifdef.

>   	pr_info("Using radix MMU under hypervisor\n");
>   
>   	pseries_lpar_register_process_table(__pa(process_tb),
>   						0, PRTB_SIZE_SHIFT - 12);
> +#endif
>   }
>   
>   #ifdef CONFIG_PPC_SMLPAR
> 

Christophe