[Xen-changelog] [xen-4.1-testing] x86: fix delta calculation in TSC deadline timer emulation

[Xen patchbot-4.1-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User David Vrabel <david.vrabel@xxxxxxxxxx>
# Date 1334169674 -3600
# Node ID 80130491806f42cfe9c8b93b755c3852ae55733d
# Parent  6f224431eca2ecea490fdcbd401942de5b20c3dd
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>
xen-unstable changeset:   25191:a95fc7decc83
xen-unstable date:        Wed Apr 11 16:49:45 2012 +0100
---


diff -r 6f224431eca2 -r 80130491806f xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c Wed Apr 04 16:09:25 2012 +0100
+++ b/xen/arch/x86/hvm/vlapic.c Wed Apr 11 19:41:14 2012 +0100
@@ -889,7 +889,6 @@ 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 */
@@ -901,12 +900,10 @@ 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);
 
@@ -940,9 +937,8 @@ 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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