From: Christoph Egger <Christoph.Egger@amd.com>
To: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: [PATCH] xen: fix performance decrease with asid assignment
Date: Tue, 12 Jun 2012 15:32:52 +0200 [thread overview]
Message-ID: <4FD74504.8090407@amd.com> (raw)
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Do not clear asid cleanbit unconditionally. This shaves
off 100 cycles from the VMRUN instruction.
Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
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Advanced Micro Devices GmbH
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Registergericht Muenchen, HRB Nr. 43632
[-- Attachment #2: xen_asid.diff --]
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diff -r 1f466caea5b7 xen/arch/x86/hvm/svm/asid.c
--- a/xen/arch/x86/hvm/svm/asid.c Fri Jun 08 15:24:29 2012 +0200
+++ b/xen/arch/x86/hvm/svm/asid.c Tue Jun 12 15:12:48 2012 +0200
@@ -63,7 +63,8 @@ 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;
}
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