On Sat, Jul 13, 2013 at 12:30:50AM -0600, Chris Friesen wrote: > 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 at 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@" Yeah probably, I think folks tend to use "/memory at 0" even if they only have a single memory node. But that does sound like a bug in kexec. > 2) lmb_reserve() should really respect the crashkernel memory limit It's been replaced in mainline, so you'd have to check what the current code does in that situation. > 3) the freescale stuff really shouldn't assume it can map things > wherever it feels like Agreed :) cheers
