The implementation of this new behavior aligns with the guidelines
outlined in the Intel SDM.
Following a power-up or RESET of an MP system, system hardware
dynamically selects one of the processors on the system bus as the BSP.
The remaining processors are designated as APs. The APs complete a
minimal self-configuration, then wait for a startup signal (a SIPI
message) from the BSP processor.
Additionally, the MP protocol is executed only after
a power-up or RESET. If the MP protocol has completed and a
BSP is chosen, subsequent INITs (either to a specific processor or
system wide) do not cause the MP protocol to be repeated. Instead, each
logical processor examines its BSP flag (in the IA32_APIC_BASE MSR) to
determine whether it should execute the BIOS boot-strap code (if it is
the BSP) or enter a wait-for-SIPI state (if it is an AP).
Cc: Guo Dong <guo.d...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Cc: Sean Rhodes <sean@starlabs.systems>
Cc: James Lu <james...@intel.com>
Cc: Gua Guo <gua....@intel.com>
Signed-off-by: Yuanhao Xie <yuanhao....@intel.com>
---
UefiCpuPkg/Library/MpInitLib/MpLib.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c
b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 737e03ffc5..ce94937e30 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -1294,7 +1294,14 @@ WakeUpAP (
if (CpuMpData->SevSnpIsEnabled && (CpuMpData->InitFlag != ApInitConfig))
{
SevSnpCreateAP (CpuMpData, -1);
} else {
- SendInitSipiSipiAllExcludingSelf ((UINT32)ExchangeInfo->BufferStart);
+ if ((CpuMpData->InitFlag == ApInitConfig) && FixedPcdGetBool
(PcdFirstTimeWakeUpAPsBySipi)) {
+ //
+ // SIPI can be used for the first time wake up after reset to reduce
boot time.
+ //
+ SendStartupIpiAllExcludingSelf ((UINT32)ExchangeInfo->BufferStart);
+ } else {
+ SendInitSipiSipiAllExcludingSelf ((UINT32)ExchangeInfo->BufferStart);
+ }
}
}
--
2.36.1.windows.1
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