15-34 Vol. 3B

MACHINE-CHECK ARCHITECTURE

GOTO LOG MCA REGISTER;

ELSE  (* It is a corrected error; continue to the next IA32_MCi_STATUS *) 

GOTO CONTINUE;

FI; UC

FI; VAL 

LOG MCA REGISTER:

SAVE IA32_MCi_STATUS;

If MISCV in IA32_MCi_STATUS 

THEN

SAVE IA32_MCi_MISC;

FI;
IF ADDRV in IA32_MCi_STATUS

THEN

SAVE IA32_MCi_ADDR;

FI;
IF CLEAR_MC_BANK = TRUE

THEN

SET all 0 to IA32_MCi_STATUS;
If MISCV in IA32_MCi_STATUS 

THEN

SET all 0 to IA32_MCi_MISC;

FI;

IF ADDRV in IA32_MCi_STATUS

THEN

SET all 0 to IA32_MCi_ADDR;

FI;

FI;
CONTINUE:

OD;

( *END FOR *)
RETURN;

(* End of MCA ERROR PROCESSING*)

15.10.4.2   Corrected Machine-Check Handler for Error Recovery

When writing a corrected machine check handler, which is invoked as a result of CMCI or called from an OS CMC 
Polling dispatcher, consider the following: 

•

The VAL (valid) flag in each IA32_MCi_STATUS register indicates whether the error information in the register 
is valid. If this flag is clear, the registers in that bank does not contain valid error information and does not need 
to be checked.

•

The CMCI or CMC polling handler is responsible for logging and clearing corrected errors. The UC flag in each 
IA32_MCi_Status register indicates whether the reported error was corrected (UC=0) or not (UC=1). 

•

When IA32_MCG_CAP [24] is one, the CMC handler is also responsible for logging and clearing uncorrected no-
action required (UCNA) errors. When the UC flag is one but the PCC, S, and AR flags are zero in the 
IA32_MCi_STATUS register, the reported error in this bank is an uncorrected no-action required (UCNA) error. 
In cases when SRAO error are signaled as UCNA error via CMCI, software can perform recovery for those errors 
identified in Table 15-15.

•

In addition to corrected errors and UCNA errors, the CMC handler optionally logs uncorrected (UC=1 and 
PCC=1), software recoverable machine check errors (UC=1, PCC=0 and S=1), but should avoid clearing those 
errors from the MC banks. Clearing these errors may result in accidentally removing these errors before these 
errors are actually handled and processed by the MCE handler for attempted software error recovery.

Example 15-5 gives pseudocode for a CMCI handler with UCR support.