Some security features depends on the page table enabling. So, This patch
is to enable the page table if page table has not been enabled during the
transition from Temporary RAM to Permanent RAM.

Note: If page table is not enabled before this point, which means the system
IA-32e Mode is not activated. Because on Intel 64 processors, IA-32e Mode
operation requires physical address extensions with 4 or 5 levels of enhanced
paging structures (see Section 4.5, "4 - Level Paging and 5 -Level Paging"
and Section 9.8, "Initializing IA-32e Mode"). So, just enable PAE page table
if CR0.PG is not set.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Zeng Star <star.zeng@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
---
 UefiCpuPkg/CpuMpPei/CpuMpPei.h   |   1 +
 UefiCpuPkg/CpuMpPei/CpuMpPei.inf |   1 +
 UefiCpuPkg/CpuMpPei/CpuPaging.c  | 215 ++++++++++++++++-----------------------
 3 files changed, 88 insertions(+), 129 deletions(-)

diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.h b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
index 0649c48d14..1b9a94e18f 100644
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.h
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
@@ -26,10 +26,11 @@
 #include <Library/ReportStatusCodeLib.h>
 #include <Library/CpuExceptionHandlerLib.h>
 #include <Library/MpInitLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/MemoryAllocationLib.h>
+#include <Library/CpuPageTableLib.h>
 
 extern EFI_PEI_PPI_DESCRIPTOR  mPeiCpuMpPpiDesc;
 
 /**
   This service retrieves the number of logical processor in the platform
diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
index 7444bdb968..865be5627e 100644
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
@@ -44,10 +44,11 @@
   CpuExceptionHandlerLib
   MpInitLib
   BaseMemoryLib
   CpuLib
   MemoryAllocationLib
+  CpuPageTableLib
 
 [Guids]
   gEdkiiMigratedFvInfoGuid                                             ## SOMETIMES_CONSUMES     ## HOB
 
 [Ppis]
diff --git a/UefiCpuPkg/CpuMpPei/CpuPaging.c b/UefiCpuPkg/CpuMpPei/CpuPaging.c
index a471f089c8..b282e1cf14 100644
--- a/UefiCpuPkg/CpuMpPei/CpuPaging.c
+++ b/UefiCpuPkg/CpuMpPei/CpuPaging.c
@@ -115,42 +115,10 @@ AllocatePageTableMemory (
   }
 
   return Address;
 }
 
-/**
-  Get the address width supported by current processor.
-
-  @retval 32      If processor is in 32-bit mode.
-  @retval 36-48   If processor is in 64-bit mode.
-
-**/
-UINTN
-GetPhysicalAddressWidth (
-  VOID
-  )
-{
-  UINT32  RegEax;
-
-  if (sizeof (UINTN) == 4) {
-    return 32;
-  }
-
-  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
-  if (RegEax >= CPUID_VIR_PHY_ADDRESS_SIZE) {
-    AsmCpuid (CPUID_VIR_PHY_ADDRESS_SIZE, &RegEax, NULL, NULL, NULL);
-    RegEax &= 0xFF;
-    if (RegEax > 48) {
-      return 48;
-    }
-
-    return (UINTN)RegEax;
-  }
-
-  return 36;
-}
-
 /**
   Get the type of top level page table.
 
   @retval Page512G  PML4 paging.
   @retval Page1G    PAE paging.
@@ -381,120 +349,91 @@ ConvertMemoryPageAttributes (
 
   return RETURN_SUCCESS;
 }
 
 /**
-  Get maximum size of page memory supported by current processor.
-
-  @param[in]   TopLevelType     The type of top level page entry.
+  Enable PAE Page Table.
 
-  @retval Page1G     If processor supports 1G page and PML4.
-  @retval Page2M     For all other situations.
+  @retval   EFI_SUCCESS           The PAE Page Table was enabled successfully.
+  @retval   EFI_OUT_OF_RESOURCES  The PAE Page Table could not be enabled due to lack of available memory.
 
 **/
-PAGE_ATTRIBUTE
-GetMaxMemoryPage (
-  IN  PAGE_ATTRIBUTE  TopLevelType
-  )
-{
-  UINT32  RegEax;
-  UINT32  RegEdx;
-
-  if (TopLevelType == Page512G) {
-    AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
-    if (RegEax >= CPUID_EXTENDED_CPU_SIG) {
-      AsmCpuid (CPUID_EXTENDED_CPU_SIG, NULL, NULL, NULL, &RegEdx);
-      if ((RegEdx & BIT26) != 0) {
-        return Page1G;
-      }
-    }
-  }
-
-  return Page2M;
-}
-
-/**
-  Create PML4 or PAE page table.
-
-  @return The address of page table.
-
-**/
-UINTN
-CreatePageTable (
+EFI_STATUS
+EnablePaePageTable (
   VOID
   )
 {
-  RETURN_STATUS         Status;
-  UINTN                 PhysicalAddressBits;
-  UINTN                 NumberOfEntries;
-  PAGE_ATTRIBUTE        TopLevelPageAttr;
-  UINTN                 PageTable;
-  PAGE_ATTRIBUTE        MaxMemoryPage;
-  UINTN                 Index;
-  UINT64                AddressEncMask;
-  UINT64                *PageEntry;
-  EFI_PHYSICAL_ADDRESS  PhysicalAddress;
-
-  TopLevelPageAttr    = (PAGE_ATTRIBUTE)GetPageTableTopLevelType ();
-  PhysicalAddressBits = GetPhysicalAddressWidth ();
-  NumberOfEntries     = (UINTN)1 << (PhysicalAddressBits -
-                                     mPageAttributeTable[TopLevelPageAttr].AddressBitOffset);
+  EFI_STATUS   Status;
+  PAGING_MODE  PagingMode;
+
+  UINTN               PageTable;
+  VOID                *Buffer;
+  UINTN               BufferSize;
+  IA32_MAP_ATTRIBUTE  MapAttribute;
+  IA32_MAP_ATTRIBUTE  MapMask;
+
+  PagingMode                  = PagingPae;
+  PageTable                   = 0;
+  Buffer                      = NULL;
+  BufferSize                  = 0;
+  MapAttribute.Uint64         = 0;
+  MapMask.Uint64              = MAX_UINT64;
+  MapAttribute.Bits.Present   = 1;
+  MapAttribute.Bits.ReadWrite = 1;
 
-  PageTable = (UINTN)AllocatePageTableMemory (1);
-  if (PageTable == 0) {
-    return 0;
+  //
+  // Get required buffer size for the pagetable that will be created.
+  // The Max size of LinearAddress for PAE is 2^32.
+  //
+  Status = PageTableMap (&PageTable, PagingMode, 0, &BufferSize, 0, SIZE_4GB, &MapAttribute, &MapMask, NULL);
+  ASSERT (Status == EFI_BUFFER_TOO_SMALL);
+  if (Status != EFI_BUFFER_TOO_SMALL) {
+    return Status;
   }
 
-  AddressEncMask  = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask);
-  AddressEncMask &= mPageAttributeTable[TopLevelPageAttr].AddressMask;
-  MaxMemoryPage   = GetMaxMemoryPage (TopLevelPageAttr);
-  PageEntry       = (UINT64 *)PageTable;
-
-  PhysicalAddress = 0;
-  for (Index = 0; Index < NumberOfEntries; ++Index) {
-    *PageEntry = PhysicalAddress | AddressEncMask | PAGE_ATTRIBUTE_BITS;
+  //
+  // Allocate required Buffer.
+  //
+  Buffer = AllocatePageTableMemory (EFI_SIZE_TO_PAGES (BufferSize));
+  ASSERT (Buffer != NULL);
+  if (Buffer == NULL) {
+    return EFI_OUT_OF_RESOURCES;
+  }
 
-    //
-    // Split the top page table down to the maximum page size supported
-    //
-    if (MaxMemoryPage < TopLevelPageAttr) {
-      Status = SplitPage (PageEntry, TopLevelPageAttr, MaxMemoryPage, TRUE);
-      ASSERT_EFI_ERROR (Status);
-    }
+  //
+  // Create PageTable in permanent memory.
+  // The Max size of LinearAddress for PAE is 2^32.
+  //
+  Status = PageTableMap (&PageTable, PagingMode, Buffer, &BufferSize, 0, LShiftU64 (1, 32), &MapAttribute, &MapMask, NULL);
+  ASSERT_EFI_ERROR (Status);
+  if (EFI_ERROR (Status) || (PageTable == 0)) {
+    return EFI_OUT_OF_RESOURCES;
+  }
 
-    if (TopLevelPageAttr == Page1G) {
-      //
-      // PDPTE[2:1] (PAE Paging) must be 0. SplitPage() might change them to 1.
-      //
-      *PageEntry &= ~(UINT64)(IA32_PG_RW | IA32_PG_U);
-    }
+  //
+  // Write the Pagetable to CR3.
+  //
+  AsmWriteCr3 (PageTable);
 
-    PageEntry       += 1;
-    PhysicalAddress += mPageAttributeTable[TopLevelPageAttr].Length;
-  }
+  //
+  // Enable CR4.PAE
+  //
+  AsmWriteCr4 (AsmReadCr4 () | BIT5);
 
-  return PageTable;
-}
+  //
+  // Enable CR0.PG
+  //
+  AsmWriteCr0 (AsmReadCr0 () | BIT31);
 
-/**
-  Setup page tables and make them work.
+  DEBUG ((
+    DEBUG_INFO,
+    "EnablePaePageTable: Created PageTable = 0x%x, BufferSize = %x\n",
+    PageTable,
+    BufferSize
+    ));
 
-**/
-VOID
-EnablePaging (
-  VOID
-  )
-{
-  UINTN  PageTable;
-
-  PageTable = CreatePageTable ();
-  ASSERT (PageTable != 0);
-  if (PageTable != 0) {
-    AsmWriteCr3 (PageTable);
-    AsmWriteCr4 (AsmReadCr4 () | BIT5);   // CR4.PAE
-    AsmWriteCr0 (AsmReadCr0 () | BIT31);  // CR0.PG
-  }
+  return Status;
 }
 
 /**
   Get the base address of current AP's stack.
 
@@ -622,10 +561,11 @@ MemoryDiscoveredPpiNotifyCallback (
 {
   EFI_STATUS              Status;
   BOOLEAN                 InitStackGuard;
   EDKII_MIGRATED_FV_INFO  *MigratedFvInfo;
   EFI_PEI_HOB_POINTERS    Hob;
+  IA32_CR0                Cr0;
 
   //
   // Paging must be setup first. Otherwise the exception TSS setup during MP
   // initialization later will not contain paging information and then fail
   // the task switch (for the sake of stack switch).
@@ -635,12 +575,29 @@ MemoryDiscoveredPpiNotifyCallback (
   if (IsIa32PaeSupported ()) {
     Hob.Raw        = GetFirstGuidHob (&gEdkiiMigratedFvInfoGuid);
     InitStackGuard = PcdGetBool (PcdCpuStackGuard);
   }
 
-  if (InitStackGuard || (Hob.Raw != NULL)) {
-    EnablePaging ();
+  //
+  // Some security features depends on the page table enabling. So, here
+  // is to enable the page table if page table has not been enabled yet.
+  // If page table is not enabled before this point, which means the system
+  // IA-32e Mode is not activated. Because on Intel 64 processors, IA-32e Mode
+  // operation requires physical address extensions with 4 or 5 levels of
+  // enhanced paging structures (see Section 4.5, "4 - Level Paging and 5 -
+  // Level Paging" and Section 9.8, "Initializing IA-32e Mode"). So, just
+  // enable PAE page table if CR0.PG is not set.
+  //
+  Cr0.UintN = AsmReadCr0 ();
+  if ((Cr0.Bits.PG == 0) && (InitStackGuard || (Hob.Raw != NULL))) {
+    ASSERT (sizeof (UINTN) == sizeof (UINT32));
+
+    Status = EnablePaePageTable ();
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_WARN, "MemoryDiscoveredPpiNotifyCallback: Failed to enable PAE page table: %r.\n", Status));
+      ASSERT_EFI_ERROR (Status);
+    }
   }
 
   Status = InitializeCpuMpWorker ((CONST EFI_PEI_SERVICES **)PeiServices);
   ASSERT_EFI_ERROR (Status);
 
-- 
2.16.2.windows.1



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1. can you please change the commit title as "UefiCpuPkg/CpuMpPei: Conditionally enable PAE paging in 32bit mode"?

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Wu, Jiaxin
> Sent: Friday, May 12, 2023 12:16 PM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Zeng, Star
> <star.zeng@intel.com>; Gerd Hoffmann <kraxel@redhat.com>; Kumar, Rahul R
> <rahul.r.kumar@intel.com>
> Subject: [edk2-devel] [PATCH v2 2/5] UefiCpuPkg/CpuMpPei: Enable PAE page
> table if CR0.PG is not set
> 
> Some security features depends on the page table enabling. So, This patch
> is to enable the page table if page table has not been enabled during the
> transition from Temporary RAM to Permanent RAM.

2. No need to emphasize paging is not enabled during temp-ram to permanent-ram migration.
We can just say "Some security features depend on the page table enabling. So, This patch
is to enable paging if it is not enabled (32bit mode)"

3. following commit message might not be needed.

> 
> Note: If page table is not enabled before this point, which means the system
> IA-32e Mode is not activated. Because on Intel 64 processors, IA-32e Mode
> operation requires physical address extensions with 4 or 5 levels of enhanced
> paging structures (see Section 4.5, "4 - Level Paging and 5 -Level Paging"
> and Section 9.8, "Initializing IA-32e Mode"). So, just enable PAE page table
> if CR0.PG is not set.
> 

> -UINTN
> -CreatePageTable (
> +EFI_STATUS
> +EnablePaePageTable (
>    VOID
>    )
>  {
> -  RETURN_STATUS         Status;
> -  UINTN                 PhysicalAddressBits;
> -  UINTN                 NumberOfEntries;
> -  PAGE_ATTRIBUTE        TopLevelPageAttr;
> -  UINTN                 PageTable;
> -  PAGE_ATTRIBUTE        MaxMemoryPage;
> -  UINTN                 Index;
> -  UINT64                AddressEncMask;
> -  UINT64                *PageEntry;
> -  EFI_PHYSICAL_ADDRESS  PhysicalAddress;
> -
> -  TopLevelPageAttr    = (PAGE_ATTRIBUTE)GetPageTableTopLevelType ();
> -  PhysicalAddressBits = GetPhysicalAddressWidth ();
> -  NumberOfEntries     = (UINTN)1 << (PhysicalAddressBits -
> -                                     mPageAttributeTable[TopLevelPageAttr].AddressBitOffset);
> +  EFI_STATUS   Status;
> +  PAGING_MODE  PagingMode;
> +
> +  UINTN               PageTable;
> +  VOID                *Buffer;
> +  UINTN               BufferSize;
> +  IA32_MAP_ATTRIBUTE  MapAttribute;
> +  IA32_MAP_ATTRIBUTE  MapMask;
> +
> +  PagingMode                  = PagingPae;

4. No need of local variable PagingMode.

> +  PageTable                   = 0;
> +  Buffer                      = NULL;
> +  BufferSize                  = 0;
> +  MapAttribute.Uint64         = 0;
> +  MapMask.Uint64              = MAX_UINT64;
> +  MapAttribute.Bits.Present   = 1;
> +  MapAttribute.Bits.ReadWrite = 1;
> 
> -  PageTable = (UINTN)AllocatePageTableMemory (1);
> -  if (PageTable == 0) {
> -    return 0;
> +  //
> +  // Get required buffer size for the pagetable that will be created.
> +  // The Max size of LinearAddress for PAE is 2^32.

5. Let's say "1:1 map 4GB in 32bit mode." Because people might say "PAE can support up to 2^36 address, why 2^32 here".

> +  // Create PageTable in permanent memory.
> +  // The Max size of LinearAddress for PAE is 2^32.

6. above comments seem to be redundant.

>    EFI_PEI_HOB_POINTERS    Hob;
> +  IA32_CR0                Cr0;
> 
>    //
>    // Paging must be setup first. Otherwise the exception TSS setup during MP
>    // initialization later will not contain paging information and then fail
>    // the task switch (for the sake of stack switch).
> @@ -635,12 +575,29 @@ MemoryDiscoveredPpiNotifyCallback (
>    if (IsIa32PaeSupported ()) {
>      Hob.Raw        = GetFirstGuidHob (&gEdkiiMigratedFvInfoGuid);
>      InitStackGuard = PcdGetBool (PcdCpuStackGuard);
>    }
> 
> -  if (InitStackGuard || (Hob.Raw != NULL)) {
> -    EnablePaging ();
> +  //
> +  // Some security features depends on the page table enabling. So, here
> +  // is to enable the page table if page table has not been enabled yet.
> +  // If page table is not enabled before this point, which means the system
> +  // IA-32e Mode is not activated. Because on Intel 64 processors, IA-32e Mode
> +  // operation requires physical address extensions with 4 or 5 levels of
> +  // enhanced paging structures (see Section 4.5, "4 - Level Paging and 5 -
> +  // Level Paging" and Section 9.8, "Initializing IA-32e Mode"). So, just
> +  // enable PAE page table if CR0.PG is not set.

7. Maybe simply say " Some security features depend on the page table enabling. So, here
is to enable paging if it is not enabled (only in 32bit mode)"

> +  //
> +  Cr0.UintN = AsmReadCr0 ();
> +  if ((Cr0.Bits.PG == 0) && (InitStackGuard || (Hob.Raw != NULL))) {
> +    ASSERT (sizeof (UINTN) == sizeof (UINT32));
> +
> +    Status = EnablePaePageTable ();
> +    if (EFI_ERROR (Status)) {
> +      DEBUG ((DEBUG_WARN, "MemoryDiscoveredPpiNotifyCallback: Failed to
> enable PAE page table: %r.\n", Status));
> +      ASSERT_EFI_ERROR (Status);

8. Shall we use "CpuDeadLoop()" if PAE paging enabling is failed? 



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