diff options
Diffstat (limited to 'UefiCpuPkg/Library/MpInitLib/MpLib.c')
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/MpLib.c | 99 |
1 files changed, 60 insertions, 39 deletions
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c index 594a035d8b..622b70ca3c 100644 --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c @@ -1044,46 +1044,67 @@ WakeUpAP ( SendInitSipiSipiAllExcludingSelf ((UINT32) ExchangeInfo->BufferStart);
}
if (CpuMpData->InitFlag == ApInitConfig) {
- //
- // The AP enumeration algorithm below is suitable for two use cases.
- //
- // (1) The check-in time for an individual AP is bounded, and APs run
- // through their initialization routines strongly concurrently. In
- // particular, the number of concurrently running APs
- // ("NumApsExecuting") is never expected to fall to zero
- // *temporarily* -- it is expected to fall to zero only when all
- // APs have checked-in.
- //
- // In this case, the platform is supposed to set
- // PcdCpuApInitTimeOutInMicroSeconds to a low-ish value (just long
- // enough for one AP to start initialization). The timeout will be
- // reached soon, and remaining APs are collected by watching
- // NumApsExecuting fall to zero. If NumApsExecuting falls to zero
- // mid-process, while some APs have not completed initialization,
- // the behavior is undefined.
- //
- // (2) The check-in time for an individual AP is unbounded, and/or APs
- // may complete their initializations widely spread out. In
- // particular, some APs may finish initialization before some APs
- // even start.
- //
- // In this case, the platform is supposed to set
- // PcdCpuApInitTimeOutInMicroSeconds to a high-ish value. The AP
- // enumeration will always take that long (except when the boot CPU
- // count happens to be maximal, that is,
- // PcdCpuMaxLogicalProcessorNumber). All APs are expected to
- // check-in before the timeout, and NumApsExecuting is assumed zero
- // at timeout. APs that miss the time-out may cause undefined
- // behavior.
- //
- TimedWaitForApFinish (
- CpuMpData,
- PcdGet32 (PcdCpuMaxLogicalProcessorNumber) - 1,
- PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds)
- );
+ if (PcdGet32 (PcdCpuBootLogicalProcessorNumber) > 0) {
+ //
+ // The AP enumeration algorithm below is suitable only when the
+ // platform can tell us the *exact* boot CPU count in advance.
+ //
+ // The wait below finishes only when the detected AP count reaches
+ // (PcdCpuBootLogicalProcessorNumber - 1), regardless of how long that
+ // takes. If at least one AP fails to check in (meaning a platform
+ // hardware bug), the detection hangs forever, by design. If the actual
+ // boot CPU count in the system is higher than
+ // PcdCpuBootLogicalProcessorNumber (meaning a platform
+ // misconfiguration), then some APs may complete initialization after
+ // the wait finishes, and cause undefined behavior.
+ //
+ TimedWaitForApFinish (
+ CpuMpData,
+ PcdGet32 (PcdCpuBootLogicalProcessorNumber) - 1,
+ MAX_UINT32 // approx. 71 minutes
+ );
+ } else {
+ //
+ // The AP enumeration algorithm below is suitable for two use cases.
+ //
+ // (1) The check-in time for an individual AP is bounded, and APs run
+ // through their initialization routines strongly concurrently. In
+ // particular, the number of concurrently running APs
+ // ("NumApsExecuting") is never expected to fall to zero
+ // *temporarily* -- it is expected to fall to zero only when all
+ // APs have checked-in.
+ //
+ // In this case, the platform is supposed to set
+ // PcdCpuApInitTimeOutInMicroSeconds to a low-ish value (just long
+ // enough for one AP to start initialization). The timeout will be
+ // reached soon, and remaining APs are collected by watching
+ // NumApsExecuting fall to zero. If NumApsExecuting falls to zero
+ // mid-process, while some APs have not completed initialization,
+ // the behavior is undefined.
+ //
+ // (2) The check-in time for an individual AP is unbounded, and/or APs
+ // may complete their initializations widely spread out. In
+ // particular, some APs may finish initialization before some APs
+ // even start.
+ //
+ // In this case, the platform is supposed to set
+ // PcdCpuApInitTimeOutInMicroSeconds to a high-ish value. The AP
+ // enumeration will always take that long (except when the boot CPU
+ // count happens to be maximal, that is,
+ // PcdCpuMaxLogicalProcessorNumber). All APs are expected to
+ // check-in before the timeout, and NumApsExecuting is assumed zero
+ // at timeout. APs that miss the time-out may cause undefined
+ // behavior.
+ //
+ TimedWaitForApFinish (
+ CpuMpData,
+ PcdGet32 (PcdCpuMaxLogicalProcessorNumber) - 1,
+ PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds)
+ );
- while (CpuMpData->MpCpuExchangeInfo->NumApsExecuting != 0) {
- CpuPause();
+ while (CpuMpData->MpCpuExchangeInfo->NumApsExecuting != 0) {
+ CpuPause();
+ }
}
} else {
//
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