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 <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Min Xu <[email protected]>
Cc: Jiewen Yao <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Jordan Justen <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Erdem Aktas <[email protected]>
Cc: Gerd Hoffmann <[email protected]>
Acked-by: Jiewen Yao <[email protected]>
Signed-off-by: Brijesh Singh <[email protected]>
---
.../X64/PeiDxeVirtualMemory.c | 34 +++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
index f146f6d61cc5..56db1e4b6ecf 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;
@@ -695,10 +696,12 @@ 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;
//
@@ -751,6 +754,22 @@ 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)
{
//
@@ -923,6 +942,21 @@ 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.
--
2.25.1
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