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.r...@amd.com>
Cc: James Bottomley <j...@linux.ibm.com>
Cc: Min Xu <min.m...@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Tom Lendacky <thomas.lenda...@amd.com>
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org>
Cc: Erdem Aktas <erdemak...@google.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Acked-by: Jiewen Yao <jiewen....@intel.com>
Acked-by: Gerd Hoffmann <kra...@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
.../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 f1485722f7cf..814f814035fa 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.
--
2.25.1
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