[LinuxBIOS] r2542 - trunk/LinuxBIOSv2/src/arch/i386/boot

Author: stepan
Date: 2007-02-01 01:44:27 +0100 (Thu, 01 Feb 2007)
New Revision: 2542

Modified:
   trunk/LinuxBIOSv2/src/arch/i386/boot/linuxbios_table.c
Log:
great check-in message:

Linuxbios boots an Opteron motherboard with 1GB memory.

Linuxbios directly loads a recent linux kernel.
The memory layout is like this:

BIOS-provided physical RAM map:
   BIOS-e820: 0000000000000000 - 0000000000000e18 (reserved)
   BIOS-e820: 0000000000000e18 - 00000000000a0000 (usable)
   BIOS-e820: 00000000000c0000 - 00000000000f0000 (usable)
   BIOS-e820: 00000000000f0000 - 00000000000f0400 (reserved)
   BIOS-e820: 00000000000f0400 - 0000000040000000 (usable)

The f0000-f0400 region contains IRQ and ACPI tables.

At some point the kernel builds a resource table containing
all physical address ranges and type of hardware the addresses
are mapped to. The table is accessible via /proc/iomem:

# cat /proc/iomem
00000000-00000e17 : reserved
00000e18-0009ffff : System RAM
000a0000-000bffff : Video RAM area
000c0000-000cbfff : Video ROM
000f0000-000fffff : System ROM
e0000000-efffffff : PCI Bus #03
    e0000000-efffffff : 0000:03:00.0
f0000000-f3ffffff : GART
f4000000-f60fffff : PCI Bus #03
    f4000000-f4ffffff : 0000:03:00.0
    f5000000-f5ffffff : 0000:03:00.0
    f6000000-f601ffff : 0000:03:00.0
f6100000-f6100fff : 0000:00:01.0
f6101000-f6101fff : 0000:00:02.0
    f6101000-f6101fff : ohci_hcd
f6102000-f6102fff : 0000:00:04.0
f6103000-f6103fff : 0000:00:07.0
    f6103000-f6103fff : sata_nv
f6104000-f6104fff : 0000:00:08.0
    f6104000-f6104fff : sata_nv
f6105000-f6105fff : 0000:00:0a.0
f6106000-f61060ff : 0000:00:02.1
f6200000-f620ffff : 0000:40:01.0

As you can see, the 00000000000f0400-0000000040000000
region is not listed.

It is not listed because the kernel unconditionally adds
"000f0000-000fffff : System ROM" first (look for
"request_resource(&iomem_resource, &system_rom_resource)"),
and then the attempt to add f0400-40000000 range fails
because of overlapping.

The kernel does not care that the range is not listed there.
Kexec does. It uses the /proc/iomem file to instruct the
kexec system call how to place the segments of a new kernel
in the physical memory. Kexec fails to start a new kernel
because it cannot locate enough physical memory.

This must be fixed either in linux or linuxbios.

Assuming that linuxbios is to be fixed, I cooked a patch
which provides this memory layout:

BIOS-provided physical RAM map:
   BIOS-e820: 0000000000000000 - 0000000000000e18 (reserved)
   BIOS-e820: 0000000000000e18 - 00000000000a0000 (usable)
   BIOS-e820: 00000000000c0000 - 00000000000f0000 (usable)
   BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
   BIOS-e820: 0000000000100000 - 0000000040000000 (usable)

The /proc/iomem contains:

# cat /proc/iomem 
00000000-00000e17 : reserved
00000e18-0009ffff : System RAM
000a0000-000bffff : Video RAM area
000c0000-000cbfff : Video ROM
000f0000-000fffff : System ROM
00100000-3fffffff : System RAM
    00100000-00203c61 : Kernel code
    00203c62-00248c3f : Kernel data
e0000000-efffffff : PCI Bus #03
    e0000000-efffffff : 0000:03:00.0
f0000000-f3ffffff : GART
f4000000-f60fffff : PCI Bus #03
    f4000000-f4ffffff : 0000:03:00.0
    f5000000-f5ffffff : 0000:03:00.0
    f6000000-f601ffff : 0000:03:00.0
f6100000-f6100fff : 0000:00:01.0
f6101000-f6101fff : 0000:00:02.0
    f6101000-f6101fff : ohci_hcd
f6102000-f6102fff : 0000:00:04.0
f6103000-f6103fff : 0000:00:07.0
    f6103000-f6103fff : sata_nv
f6104000-f6104fff : 0000:00:08.0
    f6104000-f6104fff : sata_nv
f6105000-f6105fff : 0000:00:0a.0
f6106000-f61060ff : 0000:00:02.1
f6200000-f620ffff : 0000:40:01.0

Kexec is happier with the patch.

Regards,

Signed-off-by: Roman Kononov  
Acked-by: Stefan Reinauer

Modified: trunk/LinuxBIOSv2/src/arch/i386/boot/linuxbios_table.c
===================================================================
--- trunk/LinuxBIOSv2/src/arch/i386/boot/linuxbios_table.c	2007-02-01 00:40:51 UTC (rev 2541)
+++ trunk/LinuxBIOSv2/src/arch/i386/boot/linuxbios_table.c	2007-02-01 00:44:27 UTC (rev 2542)
@@ -382,8 +382,9 @@
    	low_table_start, low_table_end - low_table_start);

/* Record the pirq table, acpi tables, and maybe the mptable */
+	table_size=rom_table_end-rom_table_start;
    lb_add_memory_range(mem, LB_MEM_TABLE, 
-		rom_table_start, rom_table_end - rom_table_start);
+		rom_table_start, table_size<0x10000?0x10000:table_size);

/* Note:
     * I assume that there is always memory at immediately after