Changeset 48567 in vbox for trunk/src/VBox/VMM/VMMR0

Timestamp:

Sep 19, 2013 10:51:40 PM (12 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

89119

Message:

CPUMR0: Avoid EFER writes whenever possible. Don't know which kernels actually set the EFER.FFXSR bit.

Location:

trunk/src/VBox/VMM/VMMR0

Files:

• CPUMR0.cpp (modified) (1 diff)
• CPUMR0A.asm (modified) (1 diff)

trunk/src/VBox/VMM/VMMR0/CPUMR0.cpp

@@ -490 +490 @@
         /* Clear MSR_K6_EFER_FFXSR or else we'll be unable to save/restore the XMM state with fxsave/fxrstor. */
         uint64_t oldMsrEFERHost = 0;
+        bool fRestoreEfer = false;
         if (pVCpu->cpum.s.fUseFlags & CPUM_USED_MANUAL_XMM_RESTORE)
         {
             oldMsrEFERHost = ASMRdMsr(MSR_K6_EFER);
-            ASMWrMsr(MSR_K6_EFER, oldMsrEFERHost & ~MSR_K6_EFER_FFXSR);
+            if (oldMsrEFERHost & MSR_K6_EFER_FFXSR)
+            {
+                ASMWrMsr(MSR_K6_EFER, oldMsrEFERHost & ~MSR_K6_EFER_FFXSR);
+                fRestoreEfer = true;
+            }
         }
         cpumR0SaveGuestRestoreHostFPUState(&pVCpu->cpum.s);
 
         /* Restore EFER MSR */
-        if (pVCpu->cpum.s.fUseFlags & CPUM_USED_MANUAL_XMM_RESTORE)
+        if (fRestoreEfer)
             ASMWrMsr(MSR_K6_EFER, oldMsrEFERHost | MSR_K6_EFER_FFXSR);
 

trunk/src/VBox/VMM/VMMR0/CPUMR0A.asm

@@ -5 +5 @@
 
 ;
-; Copyright (C) 2006-2011 Oracle Corporation
+; Copyright (C) 2006-2013 Oracle Corporation
 ;
 ; This file is part of VirtualBox Open Source Edition (OSE), as