Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Alexander Graf <agraf@suse.de>]

On 12.06.14 11:39, Paolo Bonzini wrote:
> Il 12/06/2014 11:37, Michael S. Tsirkin ha scritto:
>> Maybe just drop unnecessary stuff for new machine types?
>> Then we won't need hacks to migrate it.
>
> For any machine type it's trivial to migrate it.  All machine types 
> including old ones can disregard the migrated values.

How about a patch like this before the actual LE awareness ones? With 
this we should make virtio-serial config space completely independent of 
live migration.

Also since QEMU versions that do read these swapped values during 
migration are not bi-endian aware, we can never get into a case where a 
cross-endian save needs to be considered ;).


Alex


diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 2b647b6..73cb9b7 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -670,6 +670,7 @@ static int virtio_serial_load(QEMUFile *f, void 
*opaque, int version_id)
      uint32_t max_nr_ports, nr_active_ports, ports_map;
      unsigned int i;
      int ret;
+    uint32_t tmp;

      if (version_id > 3) {
          return -EINVAL;
@@ -685,17 +686,12 @@ static int virtio_serial_load(QEMUFile *f, void 
*opaque, int version_id)
          return 0;
      }

-    /* The config space */
-    qemu_get_be16s(f, &s->config.cols);
-    qemu_get_be16s(f, &s->config.rows);
-
-    qemu_get_be32s(f, &max_nr_ports);
-    tswap32s(&max_nr_ports);
-    if (max_nr_ports > tswap32(s->config.max_nr_ports)) {
-        /* Source could have had more ports than us. Fail migration. */
-        return -EINVAL;
-    }
+    /* Unused */
+    qemu_get_be16s(f, &tmp);
+    qemu_get_be16s(f, &tmp);
+    qemu_get_be32s(f, &tmp);

+    max_nr_ports = tswap32(s->config.max_nr_ports);
      for (i = 0; i < (max_nr_ports + 31) / 32; i++) {
          qemu_get_be32s(f, &ports_map);