Intel ARCHITECTURE IA-32 User Manual download pdf (Page 547)

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Vol. 3A 14-21

MACHINE-CHECK ARCHITECTURE

AND RIPV flag in IA32_MCG_STATUS = 0

(* execution is not restartable *)

THEN

RESTARTABILITY = FALSE;

return RESTARTABILITY to calling procedure;

FI;

Save time-stamp counter and processor ID;

Set IA32_MCi_STATUS to all 0s;

Execute serializing instruction (i.e., CPUID);

FI;

OD;

FI;

If the processor supports the machine-check architecture, the utility reads through the banks of

error-reporting registers looking for valid register entries. It then saves the values of the

IA32_MCi_STATUS, IA32_MCi_ADDR, IA32_MCi_MISC and IA32_MCG_STATUS regis-

ters for each bank that is valid. The routine minimizes processing time by recording the raw data

into a system data structure or file, reducing the overhead associated with polling. User utilities

analyze the collected data in an off-line environment.

When the MCIP flag is set in the IA32_MCG_STATUS register, a machine-check exception is

in progress and the machine-check exception handler has called the exception logging routine.

Once the logging process has been completed the exception-handling routine must determine

whether execution can be restarted, which is usually possible when damage has not occurred

(The PCC flag is clear, in the IA32_MCi_STATUS register) and when the processor can guar-

antee that execution is restartable (the RIPV flag is set in the IA32_MCG_STATUS register). If

execution cannot be restarted, the system is not recoverable and the exception-handling routine

should signal the console appropriately before returning the error status to the Operating System

kernel for subsequent shutdown.

The machine-check architecture allows buffering of exceptions from a given error-reporting

bank although the Pentium 4, Intel Xeon, and P6 family processors do not implement this

feature. The error logging routine should provide compatibility with future processors by

reading each hardware error-reporting bank's IA32_MCi_STATUS register and then writing 0s

to clear the OVER and VAL flags in this register. The error logging utility should re-read the

IA32_MCi_STATUS register for the bank ensuring that the valid bit is clear. The processor will

write the next error into the register bank and set the VAL flags.

Additional information that should be stored by the exception-logging routine includes the

processor’s time-stamp counter value, which provides a mechanism to indicate the frequency of

exceptions. A multiprocessing operating system stores the identity of the processor node incur-

ring the exception using a unique identifier, such as the processor’s APIC ID (see Section 8.8,

“Handling Interrupts”).

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