Re: [PATCH v5 4/5] powerpc/crash hp: add crash hotplug support for kexec_load

[Laurent Dufour <ldufour@linux.ibm.com>]

On 20/06/2022, 09:01:05, Sourabh Jain wrote:
> A common crash hotplug handler is used for both kexec_load and
> kexec_file_load, which is already implemented in earlier patches while
> adding support for kexec_file_load.
> 
> To enable the crash hotplug handler to work for kexec_load case the
> fdt_index attribute of kimage_arch needs to be populated with index of
> FDT segment in kexec segment array.
> 
> After loading kexec segments the FDT segment is identified by looping
> through all the kexec segments and fdt_index is updated accordingly.
> 
> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> ---
>  arch/powerpc/kexec/core_64.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
> index 6d448b55dfad..373cb46bcc0e 100644
> --- a/arch/powerpc/kexec/core_64.c
> +++ b/arch/powerpc/kexec/core_64.c
> @@ -74,6 +74,31 @@ int machine_kexec_prepare(struct kimage *image)
>  	return 0;
>  }
>  
> +#if defined(CONFIG_HOTPLUG_CPU)
> +int machine_kexec_post_load(struct kimage *kimage)
> +{
> +	int i;
> +	void *ptr;
> +	unsigned long mem;
> +
> +	if (kimage->type != KEXEC_TYPE_CRASH)
> +		return 0;
> +
> +	/* Mark fdt_index invalid */
> +	kimage->arch.fdt_index = -1;

If fdt_index should be set to -1, this should be done in
machine_kexec_prepare().  Anyway, there is no need to set it to -1 because
this image will not be registered in do_kexec_load() before the following
loop is complete.

> +
> +	for (i = 0; i < kimage->nr_segments; i++) {
> +		mem = kimage->segment[i].mem;
> +		ptr = __va(mem);
> +
> +		if (ptr && fdt_magic(ptr) == FDT_MAGIC)
> +			kimage->arch.fdt_index = i;
			break;

there is no need to check the other segments, isn't it?

Cheers,
Laurent.

> +	}
> +
> +	return 0;
> +}
> +#endif
> +
>  /* Called during kexec sequence with MMU off */
>  static notrace void copy_segments(unsigned long ind)
>  {