Re: [PATCH v2 2/9] kexec_file: Generalize kexec_add_buffer.

[Dave Young]

Hi, Thiago

On 06/14/16 at 11:59am, Thiago Jung Bauermann wrote:
> Allow architectures to specify different memory walking functions for
> kexec_add_buffer. Intel uses iomem to track reserved memory ranges,
> but PowerPC uses the memblock subsystem.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx>
> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Dave Young <dyoung@xxxxxxxxxx>
> Cc: kexec@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  include/linux/kexec.h |  3 +++
>  kernel/kexec_file.c   | 44 ++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 39 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index e8acb2b43dd9..7321043aa65a 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -315,6 +315,9 @@ int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
>  					Elf_Shdr *sechdrs, unsigned int relsec);
>  int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
>  					unsigned int relsec);
> +int __weak arch_kexec_walk_mem(unsigned int image_type, unsigned long start,
> +			       unsigned long end, bool top_down, void *data,
> +			       int (*func)(u64, u64, void *));
>  void arch_kexec_protect_crashkres(void);
>  void arch_kexec_unprotect_crashkres(void);
>  
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index b6eec7527e9f..a3ca7cfe070e 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -428,6 +428,31 @@ static int locate_mem_hole_callback(u64 start, u64 end, void *arg)
>  	return locate_mem_hole_bottom_up(start, end, kbuf);
>  }
>  
> +/**
> + * arch_kexec_walk_mem - call func(data) on free memory regions
> + * @image_type:	kimage.type
> + * @start:	Don't visit memory regions below this address.
> + * @end:	Don't visit memory regions above this address.
> + * @top_down:	Start from the highest address?
> + * @data:	Argument to pass to @func.
> + * @func:	Function to call for each memory region.
> + *
> + * Return: The memory walk will stop when func returns a non-zero value
> + * and that value will be returned. If all free regions are visited without
> + * func returning non-zero, then zero will be returned.
> + */
> +int __weak arch_kexec_walk_mem(unsigned int image_type, unsigned long start,
> +			       unsigned long end, bool top_down, void *data,
> +			       int (*func)(u64, u64, void *))
> +{
> +	if (image_type == KEXEC_TYPE_CRASH)
> +		return walk_iomem_res_desc(crashk_res.desc,
> +					   IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
> +					   start, end, data, func);
> +	else
> +		return walk_system_ram_res(start, end, data, func);
> +}
> +
>  /*
>   * Helper function for placing a buffer in a kexec segment. This assumes
>   * that kexec_mutex is held.
> @@ -441,6 +466,7 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
>  	struct kexec_segment *ksegment;
>  	struct kexec_buf buf, *kbuf;
>  	int ret;
> +	unsigned long start, end;
>  
>  	/* Currently adding segment this way is allowed only in file mode */
>  	if (!image->file_mode)
> @@ -472,14 +498,16 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
>  	kbuf->top_down = top_down;
>  
>  	/* Walk the RAM ranges and allocate a suitable range for the buffer */
> -	if (image->type == KEXEC_TYPE_CRASH)
> -		ret = walk_iomem_res_desc(crashk_res.desc,
> -				IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
> -				crashk_res.start, crashk_res.end, kbuf,
> -				locate_mem_hole_callback);
> -	else
> -		ret = walk_system_ram_res(0, -1, kbuf,
> -					  locate_mem_hole_callback);
> +	if (image->type == KEXEC_TYPE_CRASH) {
> +		start = crashk_res.start;
> +		end = crashk_res.end;
> +	} else {
> +		start = 0;
> +		end = ULONG_MAX;
> +	}

For crashk_res, start and end is global, the non-crash values are
hard coded, thus it is not necessary to pass these two in arguments.

Moving above to arch_kexec_walk_mem will make it cleaner.

> +
> +	ret = arch_kexec_walk_mem(image->type, start, end, top_down, kbuf,
> +				   locate_mem_hole_callback);
>  	if (ret != 1) {
>  		/* A suitable memory range could not be found for buffer */
>  		return -EADDRNOTAVAIL;
> -- 
> 1.9.1
> 
> 
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Thanks
Dave