x86/HVM: don't inject #DB with error code

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4133,7 +4133,7 @@ void hvm_task_switch(
         goto out;
 
     if ( (tss.trace & 1) && !exn_raised )
-        hvm_inject_hw_exception(TRAP_debug, tss_sel & 0xfff8);
+        hvm_inject_hw_exception(TRAP_debug, HVM_DELIVER_NO_ERROR_CODE);
 
     tr.attr.fields.type = 0xb; /* busy 32-bit tss */
     hvm_set_segment_register(v, x86_seg_tr, &tr);