linux-kernel - Re: [PATCH 2/8] kexec_file: Generalize kexec_add

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Message-Id: <11831785.bAnhpkoBlL@hactar>
Date:	Mon, 13 Jun 2016 16:08:19 -0300
From:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:	Dave Young <dyoung@...hat.com>
Cc:	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH 2/8] kexec_file: Generalize kexec_add_buffer.

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:
> On 06/12/16 at 12:10am, 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.
> 
> 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 
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 *))
{
	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?

-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center