From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Add support to the #VC exception handler to handle string IO. This
requires expanding the IO instruction parsing to recognize string based
IO instructions as well as preparing an un-encrypted buffer to be used
to transfer (either to or from the guest) the string contents for the IO
operation. The SW_EXITINFO2 and SW_SCRATCH fields of the GHCB are set
appropriately for the operation. Multiple VMGEXIT invocations may be
needed to complete the string IO operation.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 90 ++++++++++++++++---
 1 file changed, 76 insertions(+), 14 deletions(-)

diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
index 04e8b8aebf7d..b6ac3552894f 100644
--- a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
+++ b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
@@ -397,6 +397,26 @@ IoioExitInfo (
   ExitInfo = 0;
 
   switch (*(InstructionData->OpCodes)) {
+  //
+  // INS opcodes
+  //
+  case 0x6C:
+  case 0x6D:
+    ExitInfo |= IOIO_TYPE_INS;
+    ExitInfo |= IOIO_SEG_ES;
+    ExitInfo |= ((Regs->Rdx & 0xffff) << 16);
+    break;
+
+  //
+  // OUTS opcodes
+  //
+  case 0x6E:
+  case 0x6F:
+    ExitInfo |= IOIO_TYPE_OUTS;
+    ExitInfo |= IOIO_SEG_DS;
+    ExitInfo |= ((Regs->Rdx & 0xffff) << 16);
+    break;
+
   //
   // IN immediate opcodes
   //
@@ -445,6 +465,8 @@ IoioExitInfo (
   //
   // Single-byte opcodes
   //
+  case 0x6C:
+  case 0x6E:
   case 0xE4:
   case 0xE6:
   case 0xEC:
@@ -506,30 +528,70 @@ IoioExit (
   IN     SEV_ES_INSTRUCTION_DATA  *InstructionData
   )
 {
-  UINT64  ExitInfo1, Status;
+  UINT64   ExitInfo1, ExitInfo2, Status;
+  BOOLEAN  IsString;
 
   ExitInfo1 = IoioExitInfo (Regs, InstructionData);
   if (ExitInfo1 == 0) {
     return UnsupportedExit (Ghcb, Regs, InstructionData);
   }
 
-  if ((ExitInfo1 & IOIO_TYPE_IN) != 0) {
-    Ghcb->SaveArea.Rax = 0;
+  IsString = ((ExitInfo1 & IOIO_TYPE_STR) != 0) ? TRUE : FALSE;
+  if (IsString) {
+    UINTN  IoBytes, VmgExitBytes;
+    UINTN  GhcbCount, OpCount;
+
+    Status = 0;
+
+    IoBytes = IOIO_DATA_BYTES (ExitInfo1);
+    GhcbCount = sizeof (Ghcb->SharedBuffer) / IoBytes;
+
+    OpCount = ((ExitInfo1 & IOIO_REP) != 0) ? Regs->Rcx : 1;
+    while (OpCount) {
+      ExitInfo2 = MIN (OpCount, GhcbCount);
+      VmgExitBytes = ExitInfo2 * IoBytes;
+
+      if ((ExitInfo1 & IOIO_TYPE_IN) == 0) {
+        CopyMem (Ghcb->SharedBuffer, (VOID *) Regs->Rsi, VmgExitBytes);
+        Regs->Rsi += VmgExitBytes;
+      }
+
+      Ghcb->SaveArea.SwScratch = (UINT64) Ghcb->SharedBuffer;
+      Status = VmgExit (Ghcb, SVM_EXIT_IOIO_PROT, ExitInfo1, ExitInfo2);
+      if (Status != 0) {
+        return Status;
+      }
+
+      if ((ExitInfo1 & IOIO_TYPE_IN) != 0) {
+        CopyMem ((VOID *) Regs->Rdi, Ghcb->SharedBuffer, VmgExitBytes);
+        Regs->Rdi += VmgExitBytes;
+      }
+
+      if ((ExitInfo1 & IOIO_REP) != 0) {
+        Regs->Rcx -= ExitInfo2;
+      }
+
+      OpCount -= ExitInfo2;
+    }
   } else {
-    CopyMem (&Ghcb->SaveArea.Rax, &Regs->Rax, IOIO_DATA_BYTES (ExitInfo1));
-  }
-  GhcbSetRegValid (Ghcb, GhcbRax);
+    if ((ExitInfo1 & IOIO_TYPE_IN) != 0) {
+      Ghcb->SaveArea.Rax = 0;
+    } else {
+      CopyMem (&Ghcb->SaveArea.Rax, &Regs->Rax, IOIO_DATA_BYTES (ExitInfo1));
+    }
+    GhcbSetRegValid (Ghcb, GhcbRax);
 
-  Status = VmgExit (Ghcb, SVM_EXIT_IOIO_PROT, ExitInfo1, 0);
-  if (Status != 0) {
-    return Status;
-  }
+    Status = VmgExit (Ghcb, SVM_EXIT_IOIO_PROT, ExitInfo1, 0);
+    if (Status != 0) {
+      return Status;
+    }
 
-  if ((ExitInfo1 & IOIO_TYPE_IN) != 0) {
-    if (!GhcbIsRegValid (Ghcb, GhcbRax)) {
-      return UnsupportedExit (Ghcb, Regs, InstructionData);
+    if ((ExitInfo1 & IOIO_TYPE_IN) != 0) {
+      if (!GhcbIsRegValid (Ghcb, GhcbRax)) {
+        return UnsupportedExit (Ghcb, Regs, InstructionData);
+      }
+      CopyMem (&Regs->Rax, &Ghcb->SaveArea.Rax, IOIO_DATA_BYTES (ExitInfo1));
     }
-    CopyMem (&Regs->Rax, &Ghcb->SaveArea.Rax, IOIO_DATA_BYTES (ExitInfo1));
   }
 
   return 0;
-- 
2.27.0


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