OvmfPkg/MemEncryptSevLib: change the page state in the RMP table

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The MemEncryptSev{Set,Clear}PageEncMask() functions are used to set or
clear the memory encryption attribute in the page table. When SEV-SNP
is active, we also need to change the page state in the RMP table so that
it is in sync with the memory encryption attribute change.

Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
index f1485722f7..814f814035 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
@@ -17,6 +17,7 @@
 #include <Register/Cpuid.h>

 

 #include "VirtualMemory.h"

+#include "SnpPageStateChange.h"

 

 STATIC BOOLEAN          mAddressEncMaskChecked = FALSE;

 STATIC UINT64           mAddressEncMask;

@@ -693,10 +694,12 @@ SetMemoryEncDec (
   PAGE_MAP_AND_DIRECTORY_POINTER  *PageDirectoryPointerEntry;

   PAGE_TABLE_1G_ENTRY             *PageDirectory1GEntry;

   PAGE_TABLE_ENTRY                *PageDirectory2MEntry;

+  PHYSICAL_ADDRESS                OrigPhysicalAddress;

   PAGE_TABLE_4K_ENTRY             *PageTableEntry;

   UINT64                          PgTableMask;

   UINT64                          AddressEncMask;

   BOOLEAN                         IsWpEnabled;

+  UINTN                           OrigLength;

   RETURN_STATUS                   Status;

 

   //

@@ -749,6 +752,22 @@ SetMemoryEncDec (
 

   Status = EFI_SUCCESS;

 

+  //

+  // To maintain the security gurantees we must set the page to shared in the RMP

+  // table before clearing the memory encryption mask from the current page table.

+  //

+  // The InternalSetPageState() is used for setting the page state in the RMP table.

+  //

+  if ((Mode == ClearCBit) && MemEncryptSevSnpIsEnabled ()) {

+    InternalSetPageState (PhysicalAddress, EFI_SIZE_TO_PAGES (Length), SevSnpPageShared, FALSE);

+  }

+

+  //

+  // Save the specified length and physical address (we need it later).

+  //

+  OrigLength          = Length;

+  OrigPhysicalAddress = PhysicalAddress;

+

   while (Length != 0) {

     //

     // If Cr3BaseAddress is not specified then read the current CR3

@@ -922,6 +941,21 @@ SetMemoryEncDec (
   //

   CpuFlushTlb ();

 

+  //

+  // SEV-SNP requires that all the private pages (i.e pages mapped encrypted) must be

+  // added in the RMP table before the access.

+  //

+  // The InternalSetPageState() is used for setting the page state in the RMP table.

+  //

+  if ((Mode == SetCBit) && MemEncryptSevSnpIsEnabled ()) {

+    InternalSetPageState (

+      OrigPhysicalAddress,

+      EFI_SIZE_TO_PAGES (OrigLength),

+      SevSnpPagePrivate,

+      FALSE

+      );

+  }

+

 Done:

   //

   // Restore page table write protection, if any.