Jeremy Fitzhardinge wrote:
On Tue, 2006-05-30 at 16:41 -0400, konradr@xxxxxxxxxx wrote:
On Tue, May 30, 2006 at 12:38:01PM -0700, Jeremy Fitzhardinge wrote:
[snip]
So the MCFG entry is in the ACPI NVS region of the E820 table. Is this
bad?
Not at all. The ACPI v3.0 specs mentions that:
"ACPI NVS Memory. This range of addresses is in use or reserve by
the system and must not be used by the operating system. This
range is required to be saved and restored across an NVS sleep."
I actually misread the tables. It appears that MCFG (at 0x7f6e2e36) is
in ACPI Data (7f6d0000 - 7f6e3000). include/asm-i386/e820.h says that
memory marked as "E820_ACPI" can be reused as normal memory once the
ACPI tables have been read.
Doesn't this mean that the MCFG memory could end up being used as
general system memory? That seems bad if MCFG memory is some kind of
MMIO space. Or is the comment simply wrong?
Address where MCFG table lives is not important. What is important (and
checked) is address of MMCONFIG reported by MCFG table... Unfortunately code
does not bother with printing that address :-(
Another problem is that code has hardcoded that MMCONFIG area is 256MB large.
Unfortunately for the code PCI specification allows any power of two between 2MB
and 256MB if vendor knows that such amount of busses (from 2 to 128) will be
sufficient for system. With notebook it is quite possible that not full 8 bits
are implemented for MMCONFIG bus number.
Petr
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