x86/vvmx: add hvm_intsrc_vector support to nvmx_intr_intercept()

Under the following circumstances:

    1. L1 doesn't enable PAUSE exiting or PAUSE-loop exiting controls
    2. L2 executes PAUSE in a loop with RFLAGS.IE == 0

L1's PV IPI through event channel will never reach the target L1's vCPU
which runs L2 because nvmx_intr_intercept() doesn't know about
hvm_intsrc_vector. This leads to infinite L2 loop without nested
vmexits and can cause L1 to hang.

The issue is easily reproduced with Qemu/KVM on CentOS-7-1611 as L1
and an L2 guest with SMP.

Fix nvmx_intr_intercept() by injecting hvm_intsrc_vector irq into L1
which will cause nested vmexit.

Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>

xen/arch/x86/hvm/vmx/intr.c

@@ -188,13 +188,13 @@ static int nvmx_intr_intercept(struct vcpu *v, struct hvm_intack intack)
 
     if ( nestedhvm_vcpu_in_guestmode(v) )
     {
+        ctrl = get_vvmcs(v, PIN_BASED_VM_EXEC_CONTROL);
+        if ( !(ctrl & PIN_BASED_EXT_INTR_MASK) )
+            return 0;
+
         if ( intack.source == hvm_intsrc_pic ||
                  intack.source == hvm_intsrc_lapic )
         {
-            ctrl = get_vvmcs(v, PIN_BASED_VM_EXEC_CONTROL);
-            if ( !(ctrl & PIN_BASED_EXT_INTR_MASK) )
-                return 0;
-
             vmx_inject_extint(intack.vector, intack.source);
 
             ctrl = get_vvmcs(v, VM_EXIT_CONTROLS);
@@ -213,6 +213,11 @@ static int nvmx_intr_intercept(struct vcpu *v, struct hvm_intack intack)
 
             return 1;
         }
+        else if ( intack.source == hvm_intsrc_vector )
+        {
+            vmx_inject_extint(intack.vector, intack.source);
+            return 1;
+        }
     }
 
     return 0;