[Xen-changelog] [xen-unstable] [HVM] Fix timer interrupt underflow bug.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID decde35c6abf0bd7218df75d1f29a0b7d956c6b0
# Parent  6d7bba6443efebfd1324bf2dc29f7a1efb21ee48
[HVM] Fix timer interrupt underflow bug.

Without the patch, vlapic->intr_pending_count could become a very
small negative, causing some local APIC timer interrupts lost.

Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>
Signed-off-by: Edwin Zhai <edwin.zhai@xxxxxxxxx>
---
 xen/arch/x86/hvm/vlapic.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletion(-)

diff -r 6d7bba6443ef -r decde35c6abf xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c Sat Sep 23 14:01:53 2006 +0100
+++ b/xen/arch/x86/hvm/vlapic.c Sat Sep 23 14:04:22 2006 +0100
@@ -946,9 +946,11 @@ void vlapic_post_injection(struct vcpu *
 
         if ( vector == vlapic_lvt_vector(vlapic, APIC_LVTT) )
         {
-            vlapic->intr_pending_count[vector]--;
             if ( vlapic->intr_pending_count[vector] > 0 )
+            {
+                vlapic->intr_pending_count[vector]--;
                 vlapic_test_and_set_vector(vector, vlapic->regs + APIC_IRR);
+            }
         }
         break;
 

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