linux-kernel - Re: [PATCH v2 2/9] kexec_file: Generalize kexec_add

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Date:	Thu, 16 Jun 2016 09:58:53 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH v2 2/9] kexec_file: Generalize kexec_add_buffer.

On 06/15/16 at 01:21pm, Thiago Jung Bauermann wrote:
> Hello Dave,
> 
> Am Mittwoch, 15 Juni 2016, 15:33:02 schrieb Dave Young:
> > > @@ -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.
> 
> That's true. What about this version?
> 
> []'s
> Thiago Jung Bauermann
> IBM Linux Technology Center
> 
> 
>     kexec_file: Generalize kexec_add_buffer.
>     
>     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@...ux.vnet.ibm.com>
>     Cc: Eric Biederman <ebiederm@...ssion.com>
>     Cc: Dave Young <dyoung@...hat.com>
>     Cc: kexec@...ts.infradead.org
>     Cc: linux-kernel@...r.kernel.org
> 
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index e8acb2b43dd9..9b02f907b40a 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -315,6 +315,8 @@ 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, 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..2d066c458222 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -428,6 +428,29 @@ 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
> + * @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, bool top_down,
> +			       void *data, int (*func)(u64, u64, void *))
> +{

top_down is also not used?

Rethink about the argument name type should be better than image_type,
it is obvious in the comments and the code and simpler.

> +	if (image_type == KEXEC_TYPE_CRASH)
> +		return walk_iomem_res_desc(crashk_res.desc,
> +					   IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
> +					   crashk_res.start, crashk_res.end,
> +					   data, func);
> +	else
> +		return walk_system_ram_res(0, ULONG_MAX, data, func);
> +}
> +
>  /*
>   * Helper function for placing a buffer in a kexec segment. This assumes
>   * that kexec_mutex is held.
> @@ -472,14 +495,8 @@ 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);
> +	ret = arch_kexec_walk_mem(image->type, top_down, kbuf,
> +				   locate_mem_hole_callback);
>  	if (ret != 1) {
>  		/* A suitable memory range could not be found for buffer */
>  		return -EADDRNOTAVAIL;
>