On 07/12/2013 04:59 PM, Chris Friesen wrote:
On 07/12/2013 03:08 PM, Chris Friesen wrote:
I turned on the instrumentation in early_init_dt_scan_memory() and got
the following when jumping to the capture kernel:
memory scan node memory, reg size 16, data: 0 0 2 0,
- 0 , 200000000
That 0x200000000 matches the fact that I'm seeing 8GB of memory
available in the recovery kernel.
If I boot the original kernel with "crashkernel=224M@32M", should I
expect that only 224MB is marked as "linux,usable-memory" in the
recovery kernel?
I started looking at the kexec side of things, and I noticed something a
bit odd. In most places dealing with the device tree in kexec it accepts
either "memory" or "memory@" for the memory node name. In
add_usable_mem_property() in arch/ppc64/fs2dt.c it seems to only accept
"memory@".
Is this expected behaviour? It seems to be the same in current git
versions of kexec-tools.
On my system I see "/proc/device-tree/memory".
If I modify add_usable_mem_property() to also accept "/memory" then my
recovery kernel boots up with
physicalMemorySize = 0x10000000
which is 256MB (which is still a bit odd since I specified 224MB for the
crashkernel).
However, it then hits the BUG() call at the end of mark_bootmem() in
mm/bootmem.c.
One final thing and I'll stop replying to myself. :)
It looks like the problem is that some board-specific freescale code was
calling lmb_reserve() with a base address in the 4GB range. It seems
odd that lmb_reserve() didn't throw some kind of error when the recovery
kernel was supposed to be limited to 224MB.
Rather than try and fix the bug, I turned off the (unneeded) config
options related to the above lmb_reserve() calls and was able to
successfully access the information I needed via /dev/oldmem.
The upshot is that there seems to be a number of things that could be
improved:
1) kexec should accept "/memory" and not just "/memory@"
2) lmb_reserve() should really respect the crashkernel memory limit
3) the freescale stuff really shouldn't assume it can map things
wherever it feels like
Chris
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