On 02/22/2012 06:20 PM, Yinghai Lu wrote:

Why is MAXMEM used here?

EFI reserved area could be above 4G?

if that is the case, you will map all mmio hole below 4g.

OK, dropping this patch for now, at least from -urgent.

We really need to restrict the memory types we map, at least without
ioremap() called on them.  In theory, on x86-64, we could have a
dedicated "1:1" address for each physical address, but there is no good
reason we should ever map memory types other than RAM, ACPI and EFI by
default -- with the possible exception of the low 1 MiB legacy area.

Therefore, I don't see why on Earth we have
kernel_physical_mapping_init() create mappings for areas which are not
RAM.  It has access to the memory map at this point, so there is no
reason for it.  Unfortunately I think we still have a bunch of code
which implicitly assumes the old "PC" model with separate contiguous
memory ranges starting at 0, 1 MiB, and 4 GiB, however, there are more
and more systems where that just doesn't match reality.


	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.