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

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Date:	Tue, 03 Mar 2009 10:22:16 +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 Tue, 2009-03-03 at 09:28 +0800, Yinghai Lu wrote:
> Huang Ying wrote:
> > On Tue, 2009-03-03 at 05:38 +0800, Yinghai Lu wrote:
> >> Huang Ying wrote:
> >>> 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!
> >> what is max_low_pfn_mapped before that?
> > 
> > I don't know exactly what you mean. Can you elaborate a little?
> > 
> > 0 ~ max_low_pfn_mapped ~ max_pfn_mapped can be mapped with
> > init_memory_mapping() properly.
> > 
> > The issue of above example is that 0x3f400000 ~ 0x3f488000 is a
> > sub-range of 0x3f388000 ~ 0x3f488000, which should be mapped but is left
> > not mapped.
> what is max_low_pfn_mapped?
> 
> what is init_memory_mapping() printout?

This does not comes from a real test case. To test the changes I made, I
make efi_ioremap() being used even if the corresponding memory range is
below max_low_pfn_mapped. The dmesg of test is attached with the mail.

The printout of init_memory_mapping shows:

init_memory_mapping: 000000003f488000-000000003f4bb000                          
last_map_addr: 3f600000 end: 3f4bb000
init_memory_mapping: 000000003f590000-000000003f5bb000                          
last_map_addr: 3f600000 end: 3f5bb000
init_memory_mapping: 00000000fffb0000-00000000fffba000                          
last_map_addr: 100000000 end: fffba000

So I think it is possible to have the issue I mentioned above.

Best Regards,
Huang Ying


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