rtl8139: Use subsection to restrict migration after hotplug

rtl8139 includes a cpu_register_io_memory acquired value in it's
migration data.  This is not only unecessary, but we should treat
these values as unique to the VM instances since the value depends
on call order.  In most cases, this miraculously still works.
However, if devices are added or removed from the system, it may
represent an ordering change, which could cause the target rtl8139
device to make use of another device's cpu_register_io_memory value.
If we detect that a hot-add/remove has occured, include a subsection
to restrict migrations only to driver versions known to include this
fix.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 27 insertions, 1 deletions

diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index a8aed89..a22530c 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -495,6 +495,8 @@ typedef struct RTL8139State {
     QEMUTimer *timer;
     int64_t TimerExpire;
 
+    /* Support migration to/from old versions */
+    int rtl8139_mmio_io_addr_dummy;
 } RTL8139State;
 
 static void rtl8139_set_next_tctr_time(RTL8139State *s, int64_t current_time);
@@ -3162,6 +3164,21 @@ static int rtl8139_post_load(void *opaque, int version_id)
     return 0;
 }
 
+static bool rtl8139_hotplug_ready_needed(void *opaque)
+{
+    return qdev_machine_modified();
+}
+
+static const VMStateDescription vmstate_rtl8139_hotplug_ready ={
+    .name = "rtl8139/hotplug_ready",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void rtl8139_pre_save(void *opaque)
 {
     RTL8139State* s = opaque;
@@ -3171,6 +3188,7 @@ static void rtl8139_pre_save(void *opaque)
     rtl8139_set_next_tctr_time(s, current_time);
     s->TCTR = muldiv64(current_time - s->TCTR_base, PCI_FREQUENCY,
                        get_ticks_per_sec());
+    s->rtl8139_mmio_io_addr_dummy = s->rtl8139_mmio_io_addr;
 }
 
 static const VMStateDescription vmstate_rtl8139 = {
@@ -3223,7 +3241,7 @@ static const VMStateDescription vmstate_rtl8139 = {
 
         VMSTATE_UNUSED(4),
         VMSTATE_MACADDR(conf.macaddr, RTL8139State),
-        VMSTATE_INT32(rtl8139_mmio_io_addr, RTL8139State),
+        VMSTATE_INT32(rtl8139_mmio_io_addr_dummy, RTL8139State),
 
         VMSTATE_UINT32(currTxDesc, RTL8139State),
         VMSTATE_UINT32(currCPlusRxDesc, RTL8139State),
@@ -3252,6 +3270,14 @@ static const VMStateDescription vmstate_rtl8139 = {
 
         VMSTATE_UINT32_V(cplus_enabled, RTL8139State, 4),
         VMSTATE_END_OF_LIST()
+    },
+    .subsections = (VMStateSubsection []) {
+        {
+            .vmsd = &vmstate_rtl8139_hotplug_ready,
+            .needed = rtl8139_hotplug_ready_needed,
+        }, {
+            /* empty */
+        }
     }
 };