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

Message ID 20190813113119.14804-27-anthony.perard@citrix.com (mailing list archive)
State New, archived
Headers show
Series Specific platform to run OVMF in Xen PVH and HVM guests | expand

Commit Message

Anthony PERARD Aug. 13, 2019, 11:31 a.m. UTC 
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(-)
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Patch

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;
 }
 
 /**