[PATCH 2/9] OvmfPkg/VmgExitLib: Set the SW exit fields when performing VMGEXIT

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

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

All fields that are set in the GHCB should have their associated bit in
the GHCB ValidBitmap field set. Add support to set the bits for the
software exit information fields when performing a VMGEXIT (SwExitCode,
SwExitInfo1, SwExitInfo2).

Fixes: 61bacc0fa16f ("OvmfPkg/VmgExitLib: Implement library support for VmgExitLib in OVMF")
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/Library/VmgExitLib/VmgExitLib.c | 30 ++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitLib.c b/OvmfPkg/Library/VmgExitLib/VmgExitLib.c
index 53040cc6f649..6cf649c6101b 100644
--- a/OvmfPkg/Library/VmgExitLib/VmgExitLib.c
+++ b/OvmfPkg/Library/VmgExitLib/VmgExitLib.c
@@ -78,6 +78,32 @@ VmgExitErrorCheck (
   return Status;
 }
 
+/**
+  Marks a field at the specified offset as valid in the GHCB.
+
+  The ValidBitmap area represents the areas of the GHCB that have been marked
+  valid. Set the area of the GHCB at the specified offset as valid.
+
+  @param[in, out] Ghcb    Pointer to the Guest-Hypervisor Communication Block
+  @param[in] Offset       Offset in the GHCB to mark valid
+
+**/
+STATIC
+VOID
+GhcbSetOffsetValid (
+  IN OUT GHCB               *Ghcb,
+  IN     GHCB_QWORD_OFFSET  Offset
+  )
+{
+  UINT32  OffsetIndex;
+  UINT32  OffsetBit;
+
+  OffsetIndex = Offset / 8;
+  OffsetBit   = Offset & 0x07;
+
+  Ghcb->SaveArea.ValidBitmap[OffsetIndex] |= (1 << OffsetBit);
+}
+
 /**
   Perform VMGEXIT.
 
@@ -110,6 +136,10 @@ VmgExit (
   Ghcb->SaveArea.SwExitInfo1 = ExitInfo1;
   Ghcb->SaveArea.SwExitInfo2 = ExitInfo2;
 
+  GhcbSetOffsetValid (Ghcb, GhcbSwExitCode);
+  GhcbSetOffsetValid (Ghcb, GhcbSwExitInfo1);
+  GhcbSetOffsetValid (Ghcb, GhcbSwExitInfo2);
+
   //
   // Guest memory is used for the guest-hypervisor communication, so fence
   // the invocation of the VMGEXIT instruction to ensure GHCB accesses are
-- 
2.28.0