Hi AKASHI,

On 02/22/18 at 08:17pm, AKASHI Takahiro wrote:
> On arm64, no trampline code between old kernel and new kernel will be
> required in kexec_file implementation. This patch introduces a new
> configuration, ARCH_HAS_KEXEC_PURGATORY, and allows related code to be
> compiled in only if necessary.

Here also need the explanation about why no purgatory is needed, it would be
required for kexec if no strong reason.

> 
> Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
> Cc: Dave Young <dyo...@redhat.com>
> Cc: Vivek Goyal <vgo...@redhat.com>
> Cc: Baoquan He <b...@redhat.com>
> ---
>  arch/powerpc/Kconfig | 3 +++
>  arch/x86/Kconfig     | 3 +++
>  kernel/kexec_file.c  | 6 ++++++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 73ce5dd07642..c32a181a7cbb 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -552,6 +552,9 @@ config KEXEC_FILE
>         for kernel and initramfs as opposed to a list of segments as is the
>         case for the older kexec call.
>  
> +config ARCH_HAS_KEXEC_PURGATORY
> +     def_bool KEXEC_FILE
> +
>  config RELOCATABLE
>       bool "Build a relocatable kernel"
>       depends on PPC64 || (FLATMEM && (44x || FSL_BOOKE))
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c1236b187824..f031c3efe47e 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2019,6 +2019,9 @@ config KEXEC_FILE
>         for kernel and initramfs as opposed to list of segments as
>         accepted by previous system call.
>  
> +config ARCH_HAS_KEXEC_PURGATORY
> +     def_bool KEXEC_FILE
> +
>  config KEXEC_VERIFY_SIG
>       bool "Verify kernel signature during kexec_file_load() syscall"
>       depends on KEXEC_FILE
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index e5bcd94c1efb..990adae52151 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -26,7 +26,11 @@
>  #include <linux/vmalloc.h>
>  #include "kexec_internal.h"
>  
> +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
>  static int kexec_calculate_store_digests(struct kimage *image);
> +#else
> +static int kexec_calculate_store_digests(struct kimage *image) { return 0; };
> +#endif
>  
>  /* Architectures can provide this probe function */
>  int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
> @@ -520,6 +524,7 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
>       return 0;
>  }
>  
> +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
>  /* Calculate and store the digest of segments */
>  static int kexec_calculate_store_digests(struct kimage *image)
>  {
> @@ -1022,3 +1027,4 @@ int kexec_purgatory_get_set_symbol(struct kimage 
> *image, const char *name,
>  
>       return 0;
>  }
> +#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
> -- 
> 2.16.2
> 

Thanks
Dave

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