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

[Dave Young]

On 06/16/16 at 05:39pm, Thiago Jung Bauermann wrote:
> Am Donnerstag, 16 Juni 2016, 09:58:53 schrieb Dave Young:
> > On 06/15/16 at 01:21pm, Thiago Jung Bauermann wrote:
> > > +/**
> > > + * 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?
> 
> It's unused in the default implementation, but the powerpc implementation in patch 8 uses it:

Well, arch_kexec_walk_mem use kbuf as "data", you can even drop
"image_type" since kbuf has all you want kbuf->image->type, and
kbuf->top_down 

int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf,
			       int (*func)(u64, u64, void *))
> 
> int arch_kexec_walk_mem(unsigned int type, bool top_down, void *data,
> 			int (*func)(u64, u64, void *))
> {
> 	int ret = 0;
> 	u64 i;
> 	phys_addr_t mstart, mend;
> 
> 	if (top_down) {
> 		for_each_free_mem_range_reverse(i, NUMA_NO_NODE, 0,
> 						&mstart, &mend, NULL) {
> 			ret = func(mstart, mend, data);
> 			if (ret)
> 				break;
> 		}
> 	} else {
> 		for_each_free_mem_range(i, NUMA_NO_NODE, 0, &mstart, &mend,
> 					NULL) {
> 			ret = func(mstart, mend, data);
> 			if (ret)
> 				break;
> 		}
> 	}
> 
> 	return ret;
> }
> 
> > Rethink about the argument name type should be better than image_type,
> > it is obvious in the comments and the code and simpler.
> 
> Ok, renamed in the patch below.
> 
> []'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@xxxxxxxxxxxxxxxxxx>
>     Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
>     Cc: Dave Young <dyoung@xxxxxxxxxx>
>     Cc: kexec@xxxxxxxxxxxxxxxxxxx
>     Cc: linux-kernel@xxxxxxxxxxxxxxx
> 
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index e8acb2b43dd9..42b31f2e1d88 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 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..989647a324f2 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
> + * @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 type, bool top_down, void *data,
> +			       int (*func)(u64, u64, void *))
> +{
> +	if (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;
> 
> 
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Thanks
Dave