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@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Committed-by: Keir Fraser <keir@xen.org>
xen-unstable changeset:   25191:a95fc7decc83
xen-unstable date:        Wed Apr 11 16:49:45 2012 +0100

diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index b4142875ef480c6dd737e69dc3924fb159eb7ee1..3af41cc7c57301cc57df2af5bd2cd10c5f12a1ae 100644 (file)
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -889,7 +889,6 @@ uint64_t  vlapic_tdt_msr_get(struct vlapic *vlapic)
 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 *vlapic, uint64_t value)
     
     /* 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 *vlapic, uint64_t value)
 
     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)