[PATCH v5 26/35] OvmfPkg/XenPlatformLib: Cache result for XenDetected

["Anthony PERARD" <anthony.perard@citrix.com>]

We are going to replace XenDetected() implementation in
PlatformBootManagerLib by the one in XenPlatformLib.
PlatformBootManagerLib's implementation does cache the result of
GetFirstGuidHob(), so we do something similar in XenPlatformLib.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v4:
    - fix coding style
    
    v3:
    - new patch

 .../Library/XenPlatformLib/XenPlatformLib.c   | 20 +++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/OvmfPkg/Library/XenPlatformLib/XenPlatformLib.c b/OvmfPkg/Library/XenPlatformLib/XenPlatformLib.c
index 974a0e73f1..8f20ae2d45 100644
--- a/OvmfPkg/Library/XenPlatformLib/XenPlatformLib.c
+++ b/OvmfPkg/Library/XenPlatformLib/XenPlatformLib.c
@@ -25,14 +25,26 @@ XenGetInfoHOB (
   VOID
   )
 {
-  EFI_HOB_GUID_TYPE  *GuidHob;
+  EFI_HOB_GUID_TYPE   *GuidHob;
+  STATIC BOOLEAN      Cached = FALSE;
+  STATIC EFI_XEN_INFO *XenInfo;
+
+  //
+  // Return the cached result for the benefit of XenDetected that can be
+  // called many times.
+  //
+  if (Cached) {
+    return XenInfo;
+  }
 
   GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
   if (GuidHob == NULL) {
-    return NULL;
+    XenInfo = NULL;
+  } else {
+    XenInfo = (EFI_XEN_INFO *) GET_GUID_HOB_DATA (GuidHob);
   }
-
-  return (EFI_XEN_INFO *) GET_GUID_HOB_DATA (GuidHob);
+  Cached = TRUE;
+  return XenInfo;
 }
 
 /**
-- 
Anthony PERARD