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<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">I encountered a problem about a loop nesting occurred in manufacturing the alignment exception in machine check, trigger background is :<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">problem:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">machine checkout or critical interrupt ->…->kbox_write[for recording
<span style="color:black">last words] -</span>> memcpy(irremap_addr, src,size):_GLOBAL(memcpy)…<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">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,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">analysis:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">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
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">as follow when first enter machine check and alignment exception handler function:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> MSR:0x2 MSR:0x0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> SRR1:0x2 SRR1:0x21002<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> But the manual says SRR1 should be set to MSR(0x2),why that happened ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <img width="500" height="123" id="_x0000_i1029" src="cid:image001.jpg@01D58C0D.E496CFD0"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> Then a branch in handler function copy the SRR1 to MSR,this enble MSR[ME] and MSR[CE],system collapses.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#2F5597;mso-style-textfill-fill-color:#2F5597;mso-style-textfill-fill-alpha:100.0%">Conclusion:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 1) why the alignment exception can not be handled in machine check ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> 2) besides memcpy,any other function can cause the alignment exception ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> <span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">We still recurrent it, the line as follows:<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US"> Cpu dead lock->watch log->trigger fiq->kbox_write->memcpy->alignment exception->print last words.<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US"> but for those problems as below,what the kbox printed is empty.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">------------------kbox restart:[ 10.147594]----------------<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">kbox verify fs magic fail<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">kbox mem mabye destroyed, format it<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">kbox: load OK<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">lock-task: major[249] minor[0]<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-----start show_destroyed_kbox_mem_head----<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000000: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000010: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000020: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000030: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000040: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000050: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000060: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000070: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000080: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">00000090: 00000000 00000000 00000000 00000000 ................<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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