[edk2-devel] [PATCH V3 2/2] OvmfPkg/BaseMemEncryptTdxLib: Handle retry result of MapGPA

["sunceping" <cepingx.sun@intel.com>]

From: Ceping Sun <cepingx.sun@intel.com>

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4572

According to section 3.2 of the [GHCI] document, if the return status
of MapGPA is "TDG.VP.VMCALL_RETRY", TD must retry this operation for the
pages in the region starting at the GPA specified in R11.

In this patch, when a retry state is detected, TDVF needs to retry the
mapping with the specified address from the output results of TdVmCall.

Reference:
[GHCI]: TDX Guest-Host-Communication Interface v1.0
https://cdrdv2.intel.com/v1/dl/getContent/726790

Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Ceping Sun <cepingx.sun@intel.com>
---
 MdePkg/Include/IndustryStandard/Tdx.h         |  2 +
 .../BaseMemEncryptTdxLib/MemoryEncryption.c   | 41 ++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/MdePkg/Include/IndustryStandard/Tdx.h b/MdePkg/Include/IndustryStandard/Tdx.h
index 81df1361842b..2662761883e5 100644
--- a/MdePkg/Include/IndustryStandard/Tdx.h
+++ b/MdePkg/Include/IndustryStandard/Tdx.h
@@ -103,6 +103,8 @@
 #define TDVMCALL_REPORT_FATAL_ERR    0x10003
 #define TDVMCALL_SETUP_EVENT_NOTIFY  0x10004
 
+#define TDVMCALL_STATUS_RETRY  0x1
+
 #pragma pack(1)
 typedef struct {
   UINT64    Data[6];
diff --git a/OvmfPkg/Library/BaseMemEncryptTdxLib/MemoryEncryption.c b/OvmfPkg/Library/BaseMemEncryptTdxLib/MemoryEncryption.c
index a01dc98852b8..a71b1efbca7a 100644
--- a/OvmfPkg/Library/BaseMemEncryptTdxLib/MemoryEncryption.c
+++ b/OvmfPkg/Library/BaseMemEncryptTdxLib/MemoryEncryption.c
@@ -38,6 +38,8 @@ typedef enum {
 
 STATIC PAGE_TABLE_POOL  *mPageTablePool = NULL;
 
+#define MAX_RETRIES_PER_PAGE  3
+
 /**
   Returns boolean to indicate whether to indicate which, if any, memory encryption is enabled
 
@@ -527,6 +529,13 @@ SetOrClearSharedBit (
   EFI_STATUS                    Status;
   EDKII_MEMORY_ACCEPT_PROTOCOL  *MemoryAcceptProtocol;
 
+  UINT64  MapGpaRetryAddr;
+  UINT32  RetryCount;
+  UINT64  EndAddress;
+
+  MapGpaRetryAddr = 0;
+  RetryCount      = 0;
+
   AddressEncMask = GetMemEncryptionAddressMask ();
 
   //
@@ -540,7 +549,37 @@ SetOrClearSharedBit (
     PhysicalAddress   &= ~AddressEncMask;
   }
 
-  TdStatus = TdVmCall (TDVMCALL_MAPGPA, PhysicalAddress, Length, 0, 0, NULL);
+  EndAddress = PhysicalAddress + Length;
+  while (RetryCount < MAX_RETRIES_PER_PAGE) {
+    TdStatus = TdVmCall (TDVMCALL_MAPGPA, PhysicalAddress, Length, 0, 0, &MapGpaRetryAddr);
+    if (TdStatus != TDVMCALL_STATUS_RETRY) {
+      break;
+    }
+
+    DEBUG ((DEBUG_VERBOSE, "%a: TdVmcall(MAPGPA) Retry PhysicalAddress is %llx, MapGpaRetryAddr is %llx\n", __func__, PhysicalAddress, MapGpaRetryAddr));
+
+    if ((MapGpaRetryAddr < PhysicalAddress) || (MapGpaRetryAddr >= EndAddress)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a: TdVmcall(MAPGPA) failed with MapGpaRetryAddr(%llx) less than PhysicalAddress(%llx) or more than or equal to EndAddress(%llx) \n",
+        __func__,
+        MapGpaRetryAddr,
+        PhysicalAddress,
+        EndAddress
+        ));
+      break;
+    }
+
+    if (MapGpaRetryAddr == PhysicalAddress) {
+      RetryCount++;
+      continue;
+    }
+
+    PhysicalAddress = MapGpaRetryAddr;
+    Length          = EndAddress - PhysicalAddress;
+    RetryCount      = 0;
+  }
+
   if (TdStatus != 0) {
     DEBUG ((DEBUG_ERROR, "%a: TdVmcall(MAPGPA) failed with %llx\n", __func__, TdStatus));
     ASSERT (FALSE);
-- 
2.34.1



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