linux-kernel - Re: kexec, x86: Need a new e820 type support for kexec

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Date:	Tue, 18 Aug 2015 16:53:30 +0800
From:	Baoquan He <bhe@...hat.com>
To:	Toshi Kani <toshi.kani@...com>
Cc:	dan.j.williams@...el.com, hch@....de, linux-nvdimm@...1.01.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: kexec, x86: Need a new e820 type support for kexec

On 08/06/15 at 07:13pm, Toshi Kani wrote:
> On Thu, 2015-08-06 at 16:12 +0800, Baoquan He wrote:
> E820_PMEM cannot be emulated by the "memmap=" option.  Do you have to use
> the "memmap=" options to pass the ranges for kdump kernel?  If so, I'd
> rather ignore E820_PMEM and let it be passed as E820_RESERVED.  The kdump
> kernel can still obtain the info from NFIT if necessary.
> 
> As for the code change...
> 
> > @@ -640,6 +644,8 @@ static void cmdline_add_memmap_internal(char *cmdline, 
> > unsigned long startk,
> >  		strcat (str_mmap, "K$");
> >  	else if (type == RANGE_ACPI || type == RANGE_ACPI_NVS)
> >  		strcat (str_mmap, "K#");
> > +	else if (type == RANGE_PMEM || type == RANGE_PRAM)
> > +		strcat (str_mmap, "K!");
> 
> It should only check with RANGE_PRAM, but I do not think this change matters
> much unless you also modify the caller cmdline_add_memmap(), which has the
> following check to skip other types.  I do not think we will use legacy
> NVDIMM device as a dump device, so you may ignore RANGE_PRAM and let it be
> passed as RESERVED as well (which is likely the case I tested with).

Rethink it again, maybe it's better to pass PMEM as PRAM to kdump
kernel if user really want to use memmap way by specifying
--pass-memmap-cmdline. Then I need add the PMEM and PRAM checking here
you pointed out. Will repost with them.


> 
>                 /* Only adding memory regions of RAM and ACPI */
>                 if (type != RANGE_RAM &&
>                     type != RANGE_ACPI &&
>                     type != RANGE_ACPI_NVS)
>                         continue;
> 

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