Re: [PATCH 2/8] kexec_file: Generalize kexec_add_buffer.

On 06/13/16 at 04:08pm, Thiago Jung Bauermann wrote:

Hello Dave,

Thanks for the quick review and for your comments.

I'll separate the change to add arch_walk_system_ram and the change to add 
kexec_locate_mem_hole into different patches, and add error handling for 
KEXEC_ON_CRASH.

Am Montag, 13 Juni 2016, 15:29:39 schrieb Dave Young:

quoted

On 06/12/16 at 12:10am, Thiago Jung Bauermann wrote:

quoted

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.

Can the crashk_res be inserted to iomem_resource so that only one
weak function for system ram is needed?

Sorry, it's not clear to me what you mean by inserting crashk_res into 

Hmm, I means exporting crashkernel mem to /proc/iomem like other arches
It is just oneline:
insert_resource(&iomem_resource, &crashk_res)

But your proposal below is also fine.

iomem_resource, but I can add a bool for_crashkernel to arch_walk_system_ram 
so that it can decide which kind of memory to traverse, so the default 
implementation of kexec_file.c would be:

int __weak arch_walk_system_ram(bool for_crashkernel, unsigned long start,
				unsigned long end, bool top_down,
				void *data,
				int (*func)(u64, u64, void *))

arch_walk_mem sounds better?

{
	int ret;

	if (for_crashkernel)
		ret = walk_iomem_res_desc(crashk_res.desc,
					  IORESOURCE_SYSTEM_RAM |
					  IORESOURCE_BUSY,
					  start, end, data, func);
	else
		ret = walk_system_ram_res(start, end, data, func);

	if (ret != 1) {
		/* A suitable memory range could not be found for buffer */
		return -EADDRNOTAVAIL;
	}
}

and kexec_add_buffer / kexec_locate_mem_hole would call it with:

	if (image->type == KEXEC_TYPE_CRASH)
		ret = arch_walk_system_ram(true, crashk_res.start,
					   crashk_res.end, top_down, &buf,
					   locate_mem_hole_callback);
	else
		ret = arch_walk_system_ram(false, 0, -1, top_down, &buf,
					   locate_mem_hole_callback);

What do you think?

Sounds good, but for_crashkernel can be image_type instead. and
image->type can be passed to the arch_walk_mem function directly.

Thanks
Dave