Re: [PATCH 3/5] x86: Only direct map addresses that are marked asE820_RAM

From: Jacob Shin
Date: Tue Aug 28 2012 - 12:06:32 EST


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@xxxxxxx> 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@xxxxxxx> 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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