linux-kernel - Re: [PATCH 4/4] mm: consolidate VM_HIGH_ARCH

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Message-ID: <CABRcYm+vgD+BNYQ6H7=n6Bdhvq8QXriKx5Ksjhsx+DpYq6064g@mail.gmail.com>
Date: Tue, 6 May 2025 12:00:29 +0200
From: Florent Revest <revest@...omium.org>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Cc: catalin.marinas@....com, will@...nel.org, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, 
	hpa@...or.com, akpm@...ux-foundation.org, broonie@...nel.org, 
	thiago.bauermann@...aro.org, jackmanb@...gle.com
Subject: Re: [PATCH 4/4] mm: consolidate VM_HIGH_ARCH_* macros into parametric macros

On Tue, May 6, 2025 at 11:53 AM Florent Revest <revest@...omium.org> wrote:
>
> This reduces code duplication and chances of mistakes.
>
> Signed-off-by: Florent Revest <revest@...omium.org>
> ---
>  include/linux/mm.h | 50 ++++++++++++++--------------------------------
>  1 file changed, 15 insertions(+), 35 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b12549f0a6dce..6750020d5ea37 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -298,42 +298,22 @@ extern unsigned int kobjsize(const void *objp);
>  #define VM_MERGEABLE   0x80000000      /* KSM may merge identical pages */
>
>  #ifdef CONFIG_64BIT
> -#define VM_HIGH_ARCH_BIT_0     32      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_1     33      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_2     34      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_3     35      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_4     36      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_5     37      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_6     38      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_7     39      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_8     40      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_9     41      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_BIT_10    42      /* bit only usable on 64-bit architectures */
> -#define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
> -#define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
> -#define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
> -#define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
> -#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
> -#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5)
> -#define VM_HIGH_ARCH_6 BIT(VM_HIGH_ARCH_BIT_6)
> -#define VM_HIGH_ARCH_7 BIT(VM_HIGH_ARCH_BIT_7)
> -#define VM_HIGH_ARCH_8 BIT(VM_HIGH_ARCH_BIT_8)
> -#define VM_HIGH_ARCH_9 BIT(VM_HIGH_ARCH_BIT_9)
> -#define VM_HIGH_ARCH_10        BIT(VM_HIGH_ARCH_BIT_10)
> +#define VM_HIGH_ARCH_BIT(i)    (32+i)  /* bit only usable on 64-bit architectures */
> +#define VM_HIGH_ARCH_(i)       BIT(VM_HIGH_ARCH_BIT(i))

Argh, and of course I forgot to squash two local fixes before sending
the series out...

This should have been VM_HIGH_ARCH() here (the _ at the end is a typo)

>  #endif /* CONFIG_64BIT */
>
>  #ifdef CONFIG_ARCH_HAS_PKEYS
>  # define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0

And this should have been a VM_HIGH_ARCH_BIT(0)

... Anyway, I think it still gets the point across that it could make
some sense to change those VM_HIGH_ARCH macros.

> -# define VM_PKEY_BIT0  VM_HIGH_ARCH_0
> -# define VM_PKEY_BIT1  VM_HIGH_ARCH_1
> -# define VM_PKEY_BIT2  VM_HIGH_ARCH_2
> +# define VM_PKEY_BIT0  VM_HIGH_ARCH(0)
> +# define VM_PKEY_BIT1  VM_HIGH_ARCH(1)
> +# define VM_PKEY_BIT2  VM_HIGH_ARCH(2)
>  #if CONFIG_ARCH_PKEY_BITS > 3
> -# define VM_PKEY_BIT3  VM_HIGH_ARCH_3
> +# define VM_PKEY_BIT3  VM_HIGH_ARCH(3)
>  #else
>  # define VM_PKEY_BIT3  0
>  #endif
>  #if CONFIG_ARCH_PKEY_BITS > 4
> -# define VM_PKEY_BIT4  VM_HIGH_ARCH_4
> +# define VM_PKEY_BIT4  VM_HIGH_ARCH(4)
>  #else
>  # define VM_PKEY_BIT4  0
>  #endif
> @@ -349,7 +329,7 @@ extern unsigned int kobjsize(const void *objp);
>   * (x86). See the comments near alloc_shstk() in arch/x86/kernel/shstk.c
>   * for more details on the guard size.
>   */
> -# define VM_SHADOW_STACK       VM_HIGH_ARCH_5
> +# define VM_SHADOW_STACK       VM_HIGH_ARCH(5)
>  #endif
>
>  #if defined(CONFIG_ARM64_GCS)
> @@ -357,7 +337,7 @@ extern unsigned int kobjsize(const void *objp);
>   * arm64's Guarded Control Stack implements similar functionality and
>   * has similar constraints to shadow stacks.
>   */
> -# define VM_SHADOW_STACK       VM_HIGH_ARCH_6
> +# define VM_SHADOW_STACK       VM_HIGH_ARCH(6)
>  #endif
>
>  #ifndef VM_SHADOW_STACK
> @@ -381,8 +361,8 @@ extern unsigned int kobjsize(const void *objp);
>  #endif
>
>  #if defined(CONFIG_ARM64_MTE)
> -# define VM_MTE                VM_HIGH_ARCH_4  /* Use Tagged memory for access control */
> -# define VM_MTE_ALLOWED        VM_HIGH_ARCH_5  /* Tagged memory permitted */
> +# define VM_MTE                VM_HIGH_ARCH(4) /* Use Tagged memory for access control */
> +# define VM_MTE_ALLOWED        VM_HIGH_ARCH(5) /* Tagged memory permitted */
>  #else
>  # define VM_MTE                VM_NONE
>  # define VM_MTE_ALLOWED        VM_NONE
> @@ -393,7 +373,7 @@ extern unsigned int kobjsize(const void *objp);
>  #endif
>
>  #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> -# define VM_UFFD_MINOR         VM_HIGH_ARCH_9  /* UFFD minor faults */
> +# define VM_UFFD_MINOR         VM_HIGH_ARCH(9) /* UFFD minor faults */
>  #else /* !CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
>  # define VM_UFFD_MINOR         VM_NONE
>  #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
> @@ -406,13 +386,13 @@ extern unsigned int kobjsize(const void *objp);
>   * if KVM does not lock down the memory type.
>   */
>  #ifdef CONFIG_64BIT
> -#define VM_ALLOW_ANY_UNCACHED          VM_HIGH_ARCH_7
> +#define VM_ALLOW_ANY_UNCACHED          VM_HIGH_ARCH(7)
>  #else
>  #define VM_ALLOW_ANY_UNCACHED          VM_NONE
>  #endif
>
>  #ifdef CONFIG_64BIT
> -#define VM_DROPPABLE           VM_HIGH_ARCH_8
> +#define VM_DROPPABLE           VM_HIGH_ARCH(8)
>  #elif defined(CONFIG_PPC32)
>  #define VM_DROPPABLE           VM_ARCH_1
>  #else
> @@ -421,7 +401,7 @@ extern unsigned int kobjsize(const void *objp);
>
>  #ifdef CONFIG_64BIT
>  /* VM is sealed, in vm_flags */
> -#define VM_SEALED      VM_HIGH_ARCH_10
> +#define VM_SEALED      VM_HIGH_ARCH(10)
>  #endif
>
>  /* Bits set in the VMA until the stack is in its final location */
> --
> 2.49.0.967.g6a0df3ecc3-goog
>