[edk2-devel] [PATCH v2 04/23] UefiCpuPkg/MpInitLib: Always use AP Create if PcdSevSnpApicIds is set

["Lendacky, Thomas via groups.io" <thomas.lendacky=amd.com@groups.io>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

Currently, the first time an AP is started for an SEV-SNP guest, it relies
on the VMSA as set by the hypervisor. If the list of APIC IDs has been
retrieved, this is not necessary. Instead, use the SEV-SNP AP Create
protocol to start the AP for the first time and thereafter using the VMPL
at which the BSP is running.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf |  1 +
 UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf |  1 +
 UefiCpuPkg/Library/MpInitLib/MpLib.h          | 15 +++-
 UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c    | 21 +++++-
 UefiCpuPkg/Library/MpInitLib/MpLib.c          |  9 ++-
 UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c     | 78 ++++++++++++++++++--
 6 files changed, 112 insertions(+), 13 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
index 55e46d4a1fad..538a2146ff24 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
@@ -68,6 +68,7 @@ [Guids]
   gEfiEventExitBootServicesGuid                 ## CONSUMES  ## Event
   gEfiEventLegacyBootGuid                       ## SOMETIMES_CONSUMES  ## Event
   gEdkiiMicrocodePatchHobGuid                   ## SOMETIMES_CONSUMES  ## HOB
+  gEfiApicIdsGuid                               ## SOMETIMES_CONSUMES  ## HOB
 
 [Pcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber            ## CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
index bc3d716aa951..622baec45e2f 100644
--- a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
+++ b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf
@@ -76,3 +76,4 @@ [Ppis]
 [Guids]
   gEdkiiS3SmmInitDoneGuid
   gEdkiiMicrocodePatchHobGuid
+  gEfiApicIdsGuid                        ## SOMETIMES_CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h
index a96a6389c17d..617f7401aea8 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
@@ -2,7 +2,7 @@
   Common header file for MP Initialize Library.
 
   Copyright (c) 2016 - 2023, Intel Corporation. All rights reserved.<BR>
-  Copyright (c) 2020, AMD Inc. All rights reserved.<BR>
+  Copyright (c) 2020 - 2024, AMD Inc. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -911,6 +911,19 @@ SevSnpCreateAP (
   IN INTN         ProcessorNumber
   );
 
+/**
+  Determine if the SEV-SNP AP Create protocol should be used.
+
+  @param[in]  CpuMpData  Pointer to CPU MP Data
+
+  @retval     TRUE       Use SEV-SNP AP Create protocol
+  @retval     FALSE      Do not use SEV-SNP AP Create protocol
+**/
+BOOLEAN
+CanUseSevSnpCreateAP (
+  IN  CPU_MP_DATA  *CpuMpData
+  );
+
 /**
   Get pointer to CPU MP Data structure from GUIDed HOB.
 
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c b/UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c
index c83144285b68..0478e92317f1 100644
--- a/UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c
+++ b/UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c
@@ -2,7 +2,7 @@
 
   AMD SEV helper function.
 
-  Copyright (c) 2021, AMD Incorporated. All rights reserved.<BR>
+  Copyright (c) 2021 - 2024, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -68,3 +68,22 @@ SevSnpRmpAdjust (
   //
   return RETURN_UNSUPPORTED;
 }
+
+/**
+  Determine if the SEV-SNP AP Create protocol should be used.
+
+  @param[in]  CpuMpData  Pointer to CPU MP Data
+
+  @retval     TRUE       Use SEV-SNP AP Create protocol
+  @retval     FALSE      Do not use SEV-SNP AP Create protocol
+**/
+BOOLEAN
+CanUseSevSnpCreateAP (
+  IN  CPU_MP_DATA  *CpuMpData
+  )
+{
+  //
+  // SEV-SNP is not supported on 32-bit build.
+  //
+  return FALSE;
+}
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index cdfb570e61a0..dd8d00d54a15 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -2,7 +2,7 @@
   CPU MP Initialize Library common functions.
 
   Copyright (c) 2016 - 2022, Intel Corporation. All rights reserved.<BR>
-  Copyright (c) 2020, AMD Inc. All rights reserved.<BR>
+  Copyright (c) 2020 - 2024, AMD Inc. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -1302,9 +1302,10 @@ WakeUpAP (
       //
       // Wakeup all APs
       //   Must use the INIT-SIPI-SIPI method for initial configuration in
-      //   order to obtain the APIC ID.
+      //   order to obtain the APIC ID if not an SEV-SNP guest and the
+      //   list of APIC IDs is not available.
       //
-      if (CpuMpData->SevSnpIsEnabled && (CpuMpData->InitFlag != ApInitConfig)) {
+      if (CanUseSevSnpCreateAP (CpuMpData)) {
         SevSnpCreateAP (CpuMpData, -1);
       } else {
         if ((CpuMpData->InitFlag == ApInitConfig) && FixedPcdGetBool (PcdFirstTimeWakeUpAPsBySipi)) {
@@ -1414,7 +1415,7 @@ WakeUpAP (
         SetSevEsJumpTable (ExchangeInfo->BufferStart);
       }
 
-      if (CpuMpData->SevSnpIsEnabled && (CpuMpData->InitFlag != ApInitConfig)) {
+      if (CanUseSevSnpCreateAP (CpuMpData)) {
         SevSnpCreateAP (CpuMpData, (INTN)ProcessorNumber);
       } else {
         SendInitSipiSipi (
diff --git a/UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c b/UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c
index c9f0984f41a2..5d92c441adcd 100644
--- a/UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c
+++ b/UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c
@@ -2,7 +2,7 @@
 
   AMD SEV helper function.
 
-  Copyright (c) 2021, AMD Incorporated. All rights reserved.<BR>
+  Copyright (c) 2021 - 2024, AMD Incorporated. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -268,20 +268,55 @@ SevSnpCreateAP (
   IN INTN         ProcessorNumber
   )
 {
-  CPU_INFO_IN_HOB  *CpuInfoInHob;
-  CPU_AP_DATA      *CpuData;
-  UINTN            Index;
-  UINT32           ApicId;
+  CPU_INFO_IN_HOB    *CpuInfoInHob;
+  CPU_AP_DATA        *CpuData;
+  UINTN              Index;
+  UINTN              MaxIndex;
+  UINT32             ApicId;
+  EFI_HOB_GUID_TYPE  *GuidHob;
+  GHCB_APIC_IDS      *GhcbApicIds;
 
   ASSERT (CpuMpData->MpCpuExchangeInfo->BufferStart < 0x100000);
 
   CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
 
   if (ProcessorNumber < 0) {
-    for (Index = 0; Index < CpuMpData->CpuCount; Index++) {
+    if (CpuMpData->InitFlag == ApInitConfig) {
+      //
+      // APs have not been started, so CpuCount is not "known" yet. Use the
+      // retrieved APIC IDs to start the APs and fill out the MpLib CPU
+      // information properly. CanUseSevSnpCreateAP() guarantees we have a
+      // HOB when InitFlag is ApInitConfig.
+      //
+      GuidHob     = GetFirstGuidHob (&gEfiApicIdsGuid);
+      GhcbApicIds = (GHCB_APIC_IDS *)(*(UINTN *)GET_GUID_HOB_DATA (GuidHob));
+      MaxIndex    = MIN (GhcbApicIds->NumEntries, PcdGet32 (PcdCpuMaxLogicalProcessorNumber));
+    } else {
+      //
+      // APs have been previously started.
+      //
+      MaxIndex = CpuMpData->CpuCount;
+    }
+
+    for (Index = 0; Index < MaxIndex; Index++) {
       if (Index != CpuMpData->BspNumber) {
         CpuData = &CpuMpData->CpuData[Index];
-        ApicId  = CpuInfoInHob[Index].ApicId,
+
+        if (CpuMpData->InitFlag == ApInitConfig) {
+          ApicId = GhcbApicIds->ApicIds[Index];
+
+          //
+          // For the first boot, use the BSP register information.
+          //
+          CopyMem (
+            &CpuData->VolatileRegisters,
+            &CpuMpData->CpuData[0].VolatileRegisters,
+            sizeof (CpuData->VolatileRegisters)
+            );
+        } else {
+          ApicId = CpuInfoInHob[Index].ApicId;
+        }
+
         SevSnpCreateSaveArea (CpuMpData, CpuData, ApicId);
       }
     }
@@ -325,3 +360,32 @@ SevSnpRmpAdjust (
 
   return AsmRmpAdjust ((UINT64)PageAddress, 0, Rdx);
 }
+
+/**
+  Determine if the SEV-SNP AP Create protocol should be used.
+
+  @param[in]  CpuMpData  Pointer to CPU MP Data
+
+  @retval     TRUE       Use SEV-SNP AP Create protocol
+  @retval     FALSE      Do not use SEV-SNP AP Create protocol
+**/
+BOOLEAN
+CanUseSevSnpCreateAP (
+  IN  CPU_MP_DATA  *CpuMpData
+  )
+{
+  //
+  // The AP Create protocol is used for an SEV-SNP guest if
+  //   - The initial configuration has been performed already or
+  //   - The APIC IDs GUIDed HOB is non-zero.
+  //
+  if (!CpuMpData->SevSnpIsEnabled) {
+    return FALSE;
+  }
+
+  if ((CpuMpData->InitFlag == ApInitConfig) && (GetFirstGuidHob (&gEfiApicIdsGuid) == NULL)) {
+    return FALSE;
+  }
+
+  return TRUE;
+}
-- 
2.42.0



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