[Xen-changelog] [xen-unstable] x86: fix delta calculation in TSC deadline timer emulation

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User David Vrabel <david.vrabel@xxxxxxxxxx>
# Date 1334159385 -3600
# Node ID a95fc7decc831a01ed43c307c52287b32e7f4832
# Parent  d196634484a9f86136704f973293925445961079
x86: fix delta calculation in TSC deadline timer emulation

In the virtual LAPIC, correct the delta calculation when emulating the
TSC deadline timer.

Without this fix, XenServer (which is based on Xen 4.1) does not work
when running as an HVM guest.  dom0 fails to boot because its timer
interrupts are very delayed (by several minutes in some cases).

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Committed-by: Keir Fraser <keir@xxxxxxx>
---


diff -r d196634484a9 -r a95fc7decc83 xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c Wed Apr 11 14:14:18 2012 +0100
+++ b/xen/arch/x86/hvm/vlapic.c Wed Apr 11 16:49:45 2012 +0100
@@ -898,7 +898,6 @@ uint64_t  vlapic_tdt_msr_get(struct vlap
 void vlapic_tdt_msr_set(struct vlapic *vlapic, uint64_t value)
 {
     uint64_t guest_tsc;
-    uint64_t guest_time;
     struct vcpu *v = vlapic_vcpu(vlapic);
 
     /* may need to exclude some other conditions like vlapic->hw.disabled */
@@ -910,12 +909,10 @@ void vlapic_tdt_msr_set(struct vlapic *v
     
     /* new_value = 0, >0 && <= now, > now */
     guest_tsc = hvm_get_guest_tsc(v);
-    guest_time = hvm_get_guest_time(v);
     if ( value > guest_tsc )
     {
-        uint64_t delta = value - v->arch.hvm_vcpu.cache_tsc_offset;
-        delta = gtsc_to_gtime(v->domain, delta);
-        delta = max_t(s64, delta - guest_time, 0);
+        uint64_t delta = gtsc_to_gtime(v->domain, value - guest_tsc);
+        delta = max_t(s64, delta, 0);
 
         HVM_DBG_LOG(DBG_LEVEL_VLAPIC_TIMER, "delta[0x%016"PRIx64"]", delta);
 
@@ -949,9 +946,8 @@ void vlapic_tdt_msr_set(struct vlapic *v
 
     HVM_DBG_LOG(DBG_LEVEL_VLAPIC_TIMER,
                 "tdt_msr[0x%016"PRIx64"],"
-                " gtsc[0x%016"PRIx64"],"
-                " gtime[0x%016"PRIx64"]",
-                vlapic->hw.tdt_msr, guest_tsc, guest_time);
+                " gtsc[0x%016"PRIx64"]",
+                vlapic->hw.tdt_msr, guest_tsc);
 }
 
 static int __vlapic_accept_pic_intr(struct vcpu *v)

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