linux-kernel - Re: [PATCH 2/4] x86/boot: replace __PHYSICAL_START with LOAD_PHYSICAL

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Date: Wed, 13 Mar 2024 11:29:33 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Wei Yang <richard.weiyang@...il.com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] x86/boot: replace __PHYSICAL_START with
 LOAD_PHYSICAL_ADDR


* Wei Yang <richard.weiyang@...il.com> wrote:

> Both __PHYSICAL_START and LOAD_PHYSICAL_ADDR are defined to get aligned
> CONFIG_PHYSICAL_START, so we can replace __PHYSICAL_START with
> LOAD_PHYSICAL_ADDR. And then remove the definition of __PHYSICAL_START,
> which is only used to define __START_KERNEL.
> 
> Since <asm/boot.h> includes <asm/pgtable_types.h>, which includes
> <asm/page_types.h>, it is fine to move definition from <asm/boot.h> to
> <asm/page_types.h>.
> 
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> ---
>  arch/x86/include/asm/boot.h       | 5 -----
>  arch/x86/include/asm/page_types.h | 8 +++++---
>  2 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
> index a38cc0afc90a..12cbc57d0128 100644
> --- a/arch/x86/include/asm/boot.h
> +++ b/arch/x86/include/asm/boot.h
> @@ -6,11 +6,6 @@
>  #include <asm/pgtable_types.h>
>  #include <uapi/asm/boot.h>
>  
> -/* Physical address where kernel should be loaded. */
> -#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
> -				+ (CONFIG_PHYSICAL_ALIGN - 1)) \
> -				& ~(CONFIG_PHYSICAL_ALIGN - 1))
> -
>  /* Minimum kernel alignment, as a power of two */
>  #ifdef CONFIG_X86_64
>  # define MIN_KERNEL_ALIGN_LG2	PMD_SHIFT
> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
> index 86bd4311daf8..acc1620fd121 100644
> --- a/arch/x86/include/asm/page_types.h
> +++ b/arch/x86/include/asm/page_types.h
> @@ -31,10 +31,12 @@
>  
>  #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
>  
> -#define __PHYSICAL_START	ALIGN(CONFIG_PHYSICAL_START, \
> -				      CONFIG_PHYSICAL_ALIGN)
> +/* Physical address where kernel should be loaded. */
> +#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
> +				+ (CONFIG_PHYSICAL_ALIGN - 1)) \
> +				& ~(CONFIG_PHYSICAL_ALIGN - 1))

I agree with this simplification, but the ALIGN() expression is far easier 
to read, so please keep that one instead of the open-coded version.

Thanks,

	Ingo