From 5fe9db0f8220aa10ecb8c15f3188e024982111a7 Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Fri, 8 Mar 2024 07:30:49 -0800
Subject: OvmfPkg/BaseMemEncryptSevLib: Calculate memory size for Page State
 Change

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

Calculate the amount of memory that can be use to build the Page State
Change data (SNP_PAGE_STATE_CHANGE_INFO) instead of using a hard-coded
size. This allows for changes to the GHCB shared buffer size without
having to make changes to the page state change code.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Min Xu <min.m.xu@intel.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 .../BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c    | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
index 6a11adb06e..60b176ab14 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
@@ -133,23 +133,26 @@ BuildPageStateBuffer (
   IN EFI_PHYSICAL_ADDRESS        EndAddress,
   IN SEV_SNP_PAGE_STATE          State,
   IN BOOLEAN                     UseLargeEntry,
-  IN SNP_PAGE_STATE_CHANGE_INFO  *Info
+  IN SNP_PAGE_STATE_CHANGE_INFO  *Info,
+  IN UINTN                       InfoSize
   )
 {
   EFI_PHYSICAL_ADDRESS  NextAddress;
   UINTN                 RmpPageSize;
   UINTN                 Index;
+  UINTN                 IndexMax;
 
   // Clear the page state structure
-  SetMem (Info, sizeof (*Info), 0);
+  SetMem (Info, InfoSize, 0);
 
   Index       = 0;
+  IndexMax    = (InfoSize - sizeof (Info->Header)) / sizeof (Info->Entry[0]);
   NextAddress = EndAddress;
 
   //
   // Populate the page state entry structure
   //
-  while ((BaseAddress < EndAddress) && (Index < SNP_PAGE_STATE_MAX_ENTRY)) {
+  while ((BaseAddress < EndAddress) && (Index < IndexMax)) {
     //
     // Is this a 2MB aligned page? Check if we can use the Large RMP entry.
     //
@@ -265,7 +268,8 @@ InternalSetPageState (
                     EndAddress,
                     State,
                     UseLargeEntry,
-                    Info
+                    Info,
+                    sizeof (Ghcb->SharedBuffer)
                     );
 
     //
-- 
cgit v1.2.3