linux-kernel - Re: [PATCH] powerpc: Make virt_to

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Message-ID: <87a5uter64.fsf@mail.lhotse>
Date:   Mon, 14 Aug 2023 22:37:07 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] powerpc: Make virt_to_pfn() a static inline

Linus Walleij <linus.walleij@...aro.org> writes:
> Making virt_to_pfn() a static inline taking a strongly typed
> (const void *) makes the contract of a passing a pointer of that
> type to the function explicit and exposes any misuse of the
> macro virt_to_pfn() acting polymorphic and accepting many types
> such as (void *), (unitptr_t) or (unsigned long) as arguments
> without warnings.
...
> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
> index f2b6bf5687d0..9ee4b6d4a82a 100644
> --- a/arch/powerpc/include/asm/page.h
> +++ b/arch/powerpc/include/asm/page.h
> @@ -9,6 +9,7 @@
>  #ifndef __ASSEMBLY__
>  #include <linux/types.h>
>  #include <linux/kernel.h>
> +#include <linux/bug.h>
>  #else
>  #include <asm/types.h>
>  #endif
> @@ -119,16 +120,6 @@ extern long long virt_phys_offset;
>  #define ARCH_PFN_OFFSET		((unsigned long)(MEMORY_START >> PAGE_SHIFT))
>  #endif
>  
> -#define virt_to_pfn(kaddr)	(__pa(kaddr) >> PAGE_SHIFT)
> -#define virt_to_page(kaddr)	pfn_to_page(virt_to_pfn(kaddr))
> -#define pfn_to_kaddr(pfn)	__va((pfn) << PAGE_SHIFT)
> -
> -#define virt_addr_valid(vaddr)	({					\
> -	unsigned long _addr = (unsigned long)vaddr;			\
> -	_addr >= PAGE_OFFSET && _addr < (unsigned long)high_memory &&	\
> -	pfn_valid(virt_to_pfn(_addr));					\
> -})
> -
>  /*
>   * On Book-E parts we need __va to parse the device tree and we can't
>   * determine MEMORY_START until then.  However we can determine PHYSICAL_START
> @@ -233,6 +224,25 @@ extern long long virt_phys_offset;
>  #endif
>  #endif
>  
> +#ifndef __ASSEMBLY__
> +static inline unsigned long virt_to_pfn(const void *kaddr)
> +{
> +	return __pa(kaddr) >> PAGE_SHIFT;
> +}
> +
> +static inline const void *pfn_to_kaddr(unsigned long pfn)
> +{
> +	return (const void *)(((unsigned long)__va(pfn)) << PAGE_SHIFT);

Any reason to do it this way rather than:

+       return __va(pfn << PAGE_SHIFT);

Seems to be equivalent and much cleaner?

cheers