From: Christoph Egger <Christoph.Egger@amd.com>
Date: Wed, 13 Jun 2012 09:51:26 +0000 (+0200)
Subject: SVM: fix performance decrease with asid assignment
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~8320
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0cdb73707d054a60d9ac8cc16fb72caea0a8d395;p=xen.git

SVM: fix performance decrease with asid assignment

Do not clear asid cleanbit unconditionally. This shaves off 100 cycles
from the VMRUN instruction.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
Committed-by: Jan Beulich <jbeulich@suse.com>
---

diff --git a/xen/arch/x86/hvm/svm/asid.c b/xen/arch/x86/hvm/svm/asid.c
index 14e2abd919..3fde3631c4 100644
--- a/xen/arch/x86/hvm/svm/asid.c
+++ b/xen/arch/x86/hvm/svm/asid.c
@@ -56,7 +56,8 @@ void svm_asid_handle_vmrun(void)
         return;
     }
 
-    vmcb_set_guest_asid(vmcb, p_asid->asid);
+    if (vmcb_get_guest_asid(vmcb) != p_asid->asid)
+        vmcb_set_guest_asid(vmcb, p_asid->asid);
     vmcb->tlb_control = need_flush;
 }