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


From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice
Date: Thu, 12 Jun 2014 11:43:20 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0


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);





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