linux-kernel - Re: [PATCH] xtensa: noMMU: fix vm_get_page

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Message-ID: <ef6ee347-4248-9f06-f1a1-9f18613e97dc@arm.com>
Date:   Wed, 6 Jul 2022 10:20:48 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Max Filippov <jcmvbkbc@...il.com>, linux-xtensa@...ux-xtensa.org
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        linux-next@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] xtensa: noMMU: fix vm_get_page_prot definition

Hello Max,

I could reproduce the build failure with nommu_kc705_defconfig.

On 7/6/22 03:44, Max Filippov wrote:
> Don't define protection_map and don't use DECLARE_VM_GET_PAGE_PROT in
> noMMU configs, because in that case the definition for vm_get_page_prot
> is provided by the include/linux/mm.h

Right, a fallback (!CONFIG_MMU) stub definition is provided there.
 
> 
> Fixes: 61ab8053710f ("xtensa/mm: enable ARCH_HAS_VM_GET_PAGE_PROT")
> Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
> ---
>  arch/xtensa/mm/init.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
> index fb830ec8183c..b2587a1a7c46 100644
> --- a/arch/xtensa/mm/init.c
> +++ b/arch/xtensa/mm/init.c
> @@ -217,6 +217,7 @@ static int __init parse_memmap_opt(char *str)
>  }
>  early_param("memmap", parse_memmap_opt);
>  
> +#ifdef CONFIG_MMU
>  static const pgprot_t protection_map[16] = {
>  	[VM_NONE]					= PAGE_NONE,
>  	[VM_READ]					= PAGE_READONLY,
> @@ -236,3 +237,4 @@ static const pgprot_t protection_map[16] = {
>  	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= PAGE_SHARED_EXEC
>  };
>  DECLARE_VM_GET_PAGE_PROT
> +#endif

LGTM and fixes the build problem.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>

Reviewing CONFIG_MMU dependency for other platforms ....

* powerpc    - No CONFIG_MMU found - config MMU - bool default y
* sparc      - No CONFIG_MMU found - config MMU - bool default y
* arm64      - No CONFIG_MMU found - config MMU - bool default y
* x86        - No CONFIG_MMU found - config MMU - bool default y
* microblaze - No CONFIG_MMU found - config MMU - bool default y
* loongarch  - No CONFIG_MMU found - config MMU - bool default y
* openrisc   - No CONFIG_MMU found - config MMU - bool default y
* xtensa     - This fix here
* hexagon    - No CONFIG_MMU found - config MMU - bool default y
* parisc     - No CONFIG_MMU found - config MMU - bool default y
* alpha      - No CONFIG_MMU found - config MMU - bool default y
* nios2      - No CONFIG_MMU found - config MMU - bool default y
* riscv	     - Both protection_map[] and DECLARE_VM_GET_PAGE_PROT
               are inside CONFIG_MMU
* csky       - No CONFIG_MMU found - config MMU - bool default y
* s390       - No CONFIG_MMU found - config MMU - bool default y
* ia64       - No CONFIG_MMU found - config MMU - bool default y
* mips       - No CONFIG_MMU found - config MMU - bool default y
* m68k	     - Both protection_map[] and DECLARE_VM_GET_PAGE_PROT
               are inside CONFIG_MMU (SUN3, MOTOROLA, COLDFIRE)
* arc        - No CONFIG_MMU found - config MMU - bool default y
* arm	     - Both protection_map[] and DECLARE_VM_GET_PAGE_PROT
               are inside CONFIG_MMU
* um         - No CONFIG_MMU found - config MMU - bool default y
* sh	     - Both protection_map[] and DECLARE_VM_GET_PAGE_PROT
               needs to be moved inside CONFIG_MMU, will send a
	       patch soon.

So apart from xtensa and sh, no other platform seems to have this
CONFIG_MMU related build problem. But please do let me know if I
might have missed something.

- Anshuman