In case the number of CPUs can in increase beyond 255
due to CPU hotplug choose x2apic mode.
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
UefiCpuPkg/Library/MpInitLib/MpLib.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c
b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index e5dc852ed95f..d73b95001263 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -526,7 +526,9 @@ CollectProcessorCount (
//
// Enable x2APIC mode if
// 1. Number of CPU is greater than 255; or
- // 2. There are any logical processors reporting an Initial APIC ID of 255
or greater.
+ // 2. The platform exposed the exact *boot* CPU count to us in advance, and
+ // more than 255 logical processors are possible later, with hotplug; or
+ // 3. There are any logical processors reporting an Initial APIC ID of 255
or greater.
//
X2Apic = FALSE;
if (CpuMpData->CpuCount > 255) {
@@ -534,6 +536,10 @@ CollectProcessorCount (
// If there are more than 255 processor found, force to enable X2APIC
//
X2Apic = TRUE;
+ } else if ((PcdGet32 (PcdCpuBootLogicalProcessorNumber) > 0) &&
+ (PcdGet32 (PcdCpuMaxLogicalProcessorNumber) > 255))
+ {
+ X2Apic = TRUE;
} else {
CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
--
2.39.2
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