"boot: mem=1024M" causes only one CPU is brought up in 2.6.17-mm4

[Raid Cheng]

I installed latest mm kernel 2.6.17-mm4 on ppc64 with RHEL4-U3.
When i tried to limit the memory to 1024M by modifying yaboot.conf or
typing on the boot line, I found some error messages in dmesg log
and only one CPU is brought up by checking /proc/cpuinfo.

 But if i boot the kernel without such "mem=1024M" limitation, all 8 CPUs
 will be show in /proc/cpuinfo

  I have seen this issue both with mm1,mm2,mm3 and mm4.

  The error message printed by xmon is like (will repeat for cpu1 - cpu7):
 -------------------------------------------------------------------------------------------------------
    cpu 0x1: Vector: 300 (Data Access) at [c00000000ffbed10]
    pc: 00000000000104dc
    lr: 000000000000830c
    sp: c00000000ffbef90
   msr: 8000000000001000
   dar: c00000000ffbef88
   dsisr: a000000
   current = 0xc000000002683820
   paca    = 0xc00000000055f080
   pid   = 0, comm = swapper
  WARNING: exception is not recoverable, can't continue
  Unable to handle kernel paging request for data at address 0xc00000000ffbef88
  Faulting instruction address: 0x000104dc
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