As part of the negotiation treat ICH9_LPC_SMI_F_CPU_HOT_UNPLUG as a
subfeature of feature flag ICH9_LPC_SMI_F_CPU_HOTPLUG, so enable it only
if the other is also being negotiated.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Aaron Young <aaron.young@oracle.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 OvmfPkg/SmmControl2Dxe/SmiFeatures.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/OvmfPkg/SmmControl2Dxe/SmiFeatures.c b/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
index c9d875543205..9c205af00a08 100644
--- a/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
+++ b/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
@@ -29,6 +29,13 @@
 //
 #define ICH9_LPC_SMI_F_CPU_HOTPLUG BIT1
 
+// The following bit value stands for "enable CPU hot unplug, and inject an SMI
+// with control value ICH9_APM_CNT_CPU_HOT_UNPLUG upon hot unplug", in the
+// "etc/smi/supported-features" and "etc/smi/requested-features" fw_cfg files.
+// Can only be negotiated alongside ICH9_LPC_SMI_F_CPU_HOTPLUG.
+//
+#define ICH9_LPC_SMI_F_CPU_HOT_UNPLUG BIT2
+
 //
 // Provides a scratch buffer (allocated in EfiReservedMemoryType type memory)
 // for the S3 boot script fragment to write to and read from.
@@ -120,8 +127,18 @@ NegotiateSmiFeatures (
     // For now, we only support hotplug with SEV disabled.
     //
     RequestedFeaturesMask |= ICH9_LPC_SMI_F_CPU_HOTPLUG;
+    RequestedFeaturesMask |= ICH9_LPC_SMI_F_CPU_HOT_UNPLUG;
   }
   mSmiFeatures &= RequestedFeaturesMask;
+
+  if (!(mSmiFeatures & ICH9_LPC_SMI_F_CPU_HOTPLUG) &&
+      (mSmiFeatures & ICH9_LPC_SMI_F_CPU_HOT_UNPLUG)) {
+    DEBUG ((DEBUG_WARN, "%a CPU host-feat %x, requested mask %Lx\n",
+      __FUNCTION__, mSmiFeatures, RequestedFeaturesMask));
+
+      mSmiFeatures &= ~ICH9_LPC_SMI_F_CPU_HOT_UNPLUG;
+  }
+
   QemuFwCfgSelectItem (mRequestedFeaturesItem);
   QemuFwCfgWriteBytes (sizeof mSmiFeatures, &mSmiFeatures);
 
@@ -162,8 +179,8 @@ NegotiateSmiFeatures (
   if ((mSmiFeatures & ICH9_LPC_SMI_F_CPU_HOTPLUG) == 0) {
     DEBUG ((DEBUG_INFO, "%a: CPU hotplug not negotiated\n", __FUNCTION__));
   } else {
-    DEBUG ((DEBUG_INFO, "%a: CPU hotplug with SMI negotiated\n",
-      __FUNCTION__));
+    DEBUG ((DEBUG_INFO, "%a: CPU hotplug%s with SMI negotiated\n",
+      __FUNCTION__, (mSmiFeatures & ICH9_LPC_SMI_F_CPU_HOT_UNPLUG) ? ", unplug" : ""));
   }
 
   //
-- 
2.9.3



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