Subject: Re: [PATCH v14 09/11] x86, arm64: Add ARCH_WANT_RESERVE_CRASH_KERNEL config

From: Baoquan He <[email-masked]>
Date: Thu, 18 Feb 2021 15:31:04 +0800

On 01/30/21 at 03:10pm, Chen Zhou wrote:
> We make the functions reserve_crashkernel[_low]() as generic for
> x86 and arm64. Since reserve_crashkernel[_low]() implementations
> are quite similar on other architectures as well, we can have more
> users of this later.
> 
> So have CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL in arch/Kconfig and
> select this by X86 and ARM64.
> 
> Suggested-by: Mike Rapoport <[email-masked]>
> Suggested-by: Baoquan He <[email-masked]>
> Signed-off-by: Chen Zhou <[email-masked]>
> ---
>  arch/Kconfig        | 3 +++
>  arch/arm64/Kconfig  | 1 +
>  arch/x86/Kconfig    | 2 ++
>  kernel/crash_core.c | 7 ++-----
>  4 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 24862d15f3a3..0ca1ff5bb157 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -24,6 +24,9 @@ config KEXEC_ELF
>  config HAVE_IMA_KEXEC
>  	bool
>  
> +config ARCH_WANT_RESERVE_CRASH_KERNEL
> +	bool
> +
>  config SET_FS
>  	bool
>  
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index f39568b28ec1..09365c7ff469 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -82,6 +82,7 @@ config ARM64
>  	select ARCH_WANT_FRAME_POINTERS
>  	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
>  	select ARCH_WANT_LD_ORPHAN_WARN
> +	select ARCH_WANT_RESERVE_CRASH_KERNEL if KEXEC_CORE
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARM_AMBA
>  	select ARM_ARCH_TIMER
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 21f851179ff0..e6926fcb4a40 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -12,6 +12,7 @@ config X86_32
>  	depends on !64BIT
>  	# Options that are inherently 32-bit kernel only:
>  	select ARCH_WANT_IPC_PARSE_VERSION
> +	select ARCH_WANT_RESERVE_CRASH_KERNEL if KEXEC_CORE
>  	select CLKSRC_I8253
>  	select CLONE_BACKWARDS
>  	select GENERIC_VDSO_32
> @@ -28,6 +29,7 @@ config X86_64
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>  	select ARCH_USE_CMPXCHG_LOCKREF
> +	select ARCH_WANT_RESERVE_CRASH_KERNEL if KEXEC_CORE
>  	select HAVE_ARCH_SOFT_DIRTY
>  	select MODULES_USE_ELF_RELA
>  	select NEED_DMA_MAP_STATE
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 8479be270c0b..2c5783985db5 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -320,9 +320,7 @@ int __init parse_crashkernel_low(char *cmdline,
>   * --------- Crashkernel reservation ------------------------------
>   */
>  
> -#ifdef CONFIG_KEXEC_CORE
> -
> -#if defined(CONFIG_X86) || defined(CONFIG_ARM64)
> +#ifdef CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL
>  static int __init reserve_crashkernel_low(void)
>  {
>  #ifdef CONFIG_64BIT
> @@ -450,8 +448,7 @@ void __init reserve_crashkernel(void)
>  	crashk_res.start = crash_base;
>  	crashk_res.end   = crash_base + crash_size - 1;
>  }
> -#endif
> -#endif /* CONFIG_KEXEC_CORE */
> +#endif /* CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL */

Why don't you move the dummy reserve_crashkernel() here too?

#ifdef CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL
#ifdef CONFIG_KEXEC_CORE
...
  '...the real crashkernel reservation code...'
...
#else                     
static void __init reserve_crashkernel(void)
{
}                                               
#endif
#endif /* CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL */

Like this, you don't need those two dummy reserve_crashkernel() in x86
and arm64?

Thanks
Baoquan

>  
>  Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len)
> -- 
> 2.20.1
> 

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