linux-kernel - Re: [PATCH] Fix e820 end address with EFI

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Date:	Mon, 02 Mar 2009 15:45:59 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Brian Maly <bmaly@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix e820 end address with EFI

On Mon, 2009-03-02 at 10:51 +0800, Yinghai Lu wrote:
> On Sun, Mar 1, 2009 at 6:37 PM, Huang Ying <ying.huang@...el.com> wrote:
> >> so 64bit could use ioremap_cache() too?
> >> we may keep 32bit and 64bit a bit consistent.
> >
> > If we use ioremap_cache(), kexec runtime service will not work in kexec
> > situation, which needs EFI runtime memory area to be mapped at exact
> > same location across kexec. I think we should support kexec if possible.
> 
> 
> sure.
> 
> please don't touch max_low_pfn_mapped, because some range may not
> directly mapped under those efi run-time code

Find an issue to use init_memory_mapping() here.

If the memory range to be mapped is less than 2M, the last mapped
address may be next 2M aligned position, this may lead mapping
overlapping between memory range. Such as:

0x3f388000 - 0x3f488000: real mapped	0x3f388000 - 0x3f600000
0x3f590000 - 0x3f5bb000: real mapped	0x3f590000 - 0x3f600000

The problem is that the memory range 0x3f400000 - 0x3f590000 is left not
mapped!

Two way to fix the issue:

a) Make init_memory_mapping stopped at specified end page exactly! Even
for memory range smaller than 2M.

b) init_memory_mapping maps all underlying pages when split large
mapping.

What do you think about that?

Best Regards,
Huang Ying

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