linux-kernel - Re: [PATCH 3/5] x86: Only direct map addresses that are marked as E820

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Date:	Tue, 28 Aug 2012 11:06:31 -0500
From:	Jacob Shin <jacob.shin@....com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	X86-ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Tejun Heo <tj@...nel.org>,
	Dave Young <dyoung@...hat.com>,
	Chao Wang <chaowang@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [PATCH 3/5] x86: Only direct map addresses that are marked as
 E820_RAM

On Fri, Aug 24, 2012 at 09:54:04PM -0700, Yinghai Lu wrote:
> On Fri, Aug 24, 2012 at 9:24 PM, Jacob Shin <jacob.shin@....com> wrote:
> > On Fri, Aug 24, 2012 at 06:07:01PM -0700, Yinghai Lu wrote:
> >> On Fri, Aug 24, 2012 at 4:55 PM, Jacob Shin <jacob.shin@....com> wrote:
> >>
> >> looks like you could avoid add pfn_mapped[] array.
> >>
> >> pfn_range_is_mapped() should be
> >> check max_low_pfn_mapped, max_pfn_mapped with
> >> e820_all_mapped(start, end, E820_RAM).
> >
> > Hmm .. I guess that could work .. but what about EFI code that keys off of
> > EFI memory map? Does the EFI code update e820 and mark as E820_RAM whatever
> > ranges that it calls init_memory_mapping on (via efi_ioremap?)
> 
> they are converted to e820 memmap before init_memory_mapping is called.

Yinghai, looking into this further on my EFI enabled machine, there is a
memory range where:

- e820 marks it as E820_RESERVED
- EFI memory map marks it as EFI_RUNTIME_SERVICES_DATA

During EFI init, the range is added (redundantly) to e820 as E820_RESERVED,
but during efi_enter_virtual_mode, direct mappings are created for the
range with a call to efi_ioremap.

Another such region is EFI_RUNTIME_SERVICES_CODE which is marked as
ACPI NVS.

So these are not E820_RAM, but direct mapped by EFI code path .. what do
we do here? I think we should just stick with keeping the pfn_mapped[]
array .. no?

-Jacob

> 
> Thanks
> 
> Yinghai
> 

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