On Mar 15, 2006, at 1:31 PM, Vivek Goyal wrote:
Hi,
Is there a reason why "start" and "end" field of "struct resource"
are of
type unsigned long. My understanding is that "struct resource" can
be used
to represent any system resource including physical memory. But
unsigned
long is not suffcient to represent memory more than 4GB on PAE
systems.
Currently /proc/iomem exports physical memory also apart from io
device
memory. But on i386, it truncates any memory more than 4GB. This leads
to problems for kexec/kdump.
- Kexec reads /proc/iomem to determine the system memory layout and
prepares
a memory map based on that and passes it to the kernel being
kexeced. Given
the fact that memory more than 4GB has been truncated, new kernel
never
gets to see and use that memory.
- Kdump also reads /proc/iomem to determine the physical memory
layout of
the system and encodes this informaiton in ELF headers. After a
crash
new kernel parses these ELF headers being used by previous kernel
and
vmcore is prepared accordingly. As memory more than 4GB has been
truncated,
kdump never sees that memory and never prepares ELF headers for
it. Hence
vmcore is truncated and limited to 4GB even if there is more
physical
memory in the system.
One of the possible solutions to this problem is that expand the size
of "start" and "end" to "unsigned long long". But whole of the PCI and
driver code has been written assuming start and end to be unsigned
long
and compiler starts throwing warnings.
I am attaching a prototype patch which does minimal changes to make
memory
more than 4GB appear in /proc/iomem. It does not take care of
modifying
in tree drivers to supress warnings.
Looking for your suggestion what's the best way to handle this
issue. If
above approach seems reasonable then I can go ahead and do the changes
for in tree drivers to handle the warnings.
Thanks
Vivek
-
Your patch is insufficient. You really need to audit all the users
of "struct resource". If you search the lkml archives you will see
that Deepak Saxena, GregKH, and myself have taken stabs at this. You
should start with Greg's patch which I'm guessing is rather out of
date now.
- kumar
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
