hv: init percpu_list in hv_synic_alloc()

commit 3c7630d3 upstream.

Initializing hv_context.percpu_list in hv_synic_alloc() helps to prevent a
crash in percpu_channel_enq() when not all CPUs were online during
initialization and it naturally belongs there.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/hv/hv.c

@@ -295,6 +295,8 @@ int hv_synic_alloc(void)
 			pr_err("Unable to allocate post msg page\n");
 			goto err;
 		}
+
+		INIT_LIST_HEAD(&hv_context.percpu_list[cpu]);
 	}
 
 	return 0;
@@ -386,8 +388,6 @@ void hv_synic_init(void *arg)
 	 */
 	rdmsrl(HV_X64_MSR_VP_INDEX, vp_index);
 	hv_context.vp_index[cpu] = (u32)vp_index;
-
-	INIT_LIST_HEAD(&hv_context.percpu_list[cpu]);
 	return;
 }