From: Bhavana Nagendra <bnagendr@redhat.com>
Date: Thu, 17 Jan 2008 15:48:47 -0500
Subject: [xen] x86: more improved TPR/CR8 virtualization
Message-id: 20080117204848.1520.51965.sendpatchset@localhost.localdomain
O-Subject: [RHEL5.2 PATCH] svm.c snippet for Improved TPR/CR8 virtualization in Xen
Bugzilla: 251985

Resolves BZ 251985

I'm posting the svm.c changes to the TPR/CR8 separately per DonZ's request
as he had already incorporated the original patch into -69 build.  I've
re-tested on 2 socket Barcelona with WinXP64 guest and here are the results.
Still good, but the margins are bit in line with what I'd expect.

With the combined CR8 patch, the number of CR8 intercepts dropped from
7814084 to 8176 during WinXP 64-bit boot up.

Please ACK.

Acked-by: Don Dutile <ddutile@redhat.com>
Acked-by: "Stephen C. Tweedie" <sct@redhat.com>
Acked-by: Bill Burns <bburns@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>

diff --git a/arch/x86/hvm/svm/svm.c b/arch/x86/hvm/svm/svm.c
index 31359a3..163a6cf 100644
--- a/arch/x86/hvm/svm/svm.c
+++ b/arch/x86/hvm/svm/svm.c
@@ -2395,6 +2395,16 @@ asmlinkage void svm_vmexit_handler(struct cpu_user_regs *regs)
     struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
     int inst_len, rc;
 
+    /*
+     * Before doing anything else, we need to sync up the VLAPIC's TPR with
+     * SVM's vTPR if CR8 writes are currently disabled.  It's OK if the
+     * guest doesn't touch the CR8 (e.g. 32-bit Windows) because we update
+     * the vTPR on MMIO writes to the TPR
+     */
+    if ( !(vmcb->cr_intercepts & CR_INTERCEPT_CR8_WRITE) )
+        vlapic_set_reg(vcpu_vlapic(v), APIC_TASKPRI,
+                       (vmcb->vintr.fields.tpr & 0x0F) << 4);
+ 
     exit_reason = vmcb->exitcode;
 
     HVMTRACE_2D(VMEXIT, v, vmcb->rip, exit_reason);