Hi,
I encountered a problem about a loop nesting occurred in manufacturing the
alignment exception in machine check, trigger background is :
problem:
machine checkout or critical interrupt ->...->kbox_write[for recording last
words] -> memcpy(irremap_addr, src,size):_GLOBAL(memcpy)...
when we enter memcpy,a command 'dcbz r11,r6' will cause a alignment exception,
in this situation,r11 loads the ioremap address,which leads to the alignment
exception,
then the command can not be process successfully,as we still in machine
check.at the end ,it triggers a new irq machine check in irq handler function,a
loop nesting begins.
analysis:
We have analysed a lot,but it still can not come to a reasonable description,in
common,the alignment triggered in machine check context can still be collected
into the Kbox
after alignment exception be handled by handler function, but how does the
machine checkout can be triggered in the handler fucntion for any causes? We
print relevant registers
as follow when first enter machine check and alignment exception handler
function:
MSR:0x2 MSR:0x0
SRR1:0x2 SRR1:0x21002
But the manual says SRR1 should be set to MSR(0x2),why that happened ?
[cid:image001.jpg@01D58C0D.E496CFD0]
Then a branch in handler function copy the SRR1 to MSR,this enble
MSR[ME] and MSR[CE],system collapses.
Conclusion:
1) why the alignment exception can not be handled in machine check ?
2) besides memcpy,any other function can cause the alignment
exception ?
We still recurrent it, the line as follows:
Cpu dead lock->watch log->trigger fiq->kbox_write->memcpy->alignment
exception->print last words.
but for those problems as below,what the kbox printed is empty.
------------------kbox restart:[ 10.147594]----------------
kbox verify fs magic fail
kbox mem mabye destroyed, format it
kbox: load OK
lock-task: major[249] minor[0]
-----start show_destroyed_kbox_mem_head----
00000000: 00000000 00000000 00000000 00000000 ................
00000010: 00000000 00000000 00000000 00000000 ................
00000020: 00000000 00000000 00000000 00000000 ................
00000030: 00000000 00000000 00000000 00000000 ................
00000040: 00000000 00000000 00000000 00000000 ................
00000050: 00000000 00000000 00000000 00000000 ................
00000060: 00000000 00000000 00000000 00000000 ................
00000070: 00000000 00000000 00000000 00000000 ................
00000080: 00000000 00000000 00000000 00000000 ................
00000090: 00000000 00000000 00000000 00000000 ................
