commit 08f432aa3eb62d6d781eaa085e161e8628a9a538
author David Gibson <david@gibson.dropbear.id.au> Fri Dec 19 14:57:27 2014 +1100
committer Amit Shah <amit.shah@redhat.com> Mon Jan 05 12:50:27 2015 +0530
tree 3c888d6b0e8e568ac6be729b94102de1e1f8f871
parent f2f6e00b2e27b65edaa6ce5cb01770c973cbf8fb

virtio-serial: Don't keep a persistent copy of config space

The 'config' field in the VirtIOSerial structure keeps a copy of the virtio
console's config space as visible to the guest, that is to say, in guest
endianness.  This is fiddly to maintain, because on some targets, such as
powerpc, the "guest endianness" can change when a new guest OS boots.

In fact, there's no need to maintain such a guest view of config space -
instead we can reconstruct it from host-format data when it is accessed
with get_config.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Amit Shah <amit.shah@redhat.com>

hw/char/virtio-serial-bus.c

diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index e013504..37a6f44 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -482,10 +482,14 @@
 /* Guest requested config info */
 static void get_config(VirtIODevice *vdev, uint8_t *config_data)
 {
-    VirtIOSerial *vser;
+    VirtIOSerial *vser = VIRTIO_SERIAL(vdev);
+    struct virtio_console_config *config =
+        (struct virtio_console_config *)config_data;
 
-    vser = VIRTIO_SERIAL(vdev);
-    memcpy(config_data, &vser->config, sizeof(struct virtio_console_config));
+    config->cols = 0;
+    config->rows = 0;
+    config->max_nr_ports = virtio_tswap32(vdev,
+                                          vser->serial.max_virtserial_ports);
 }
 
 static void guest_reset(VirtIOSerial *vser)
@@ -533,10 +537,6 @@
 
     vser = VIRTIO_SERIAL(vdev);
     guest_reset(vser);
-
-    /* In case we have switched endianness */
-    vser->config.max_nr_ports =
-        virtio_tswap32(vdev, vser->serial.max_virtserial_ports);
 }
 
 static void virtio_serial_save(QEMUFile *f, void *opaque)
@@ -551,12 +551,13 @@
     VirtIOSerialPort *port;
     uint32_t nr_active_ports;
     unsigned int i, max_nr_ports;
+    struct virtio_console_config config;
 
-    /* The config space */
-    qemu_put_be16s(f, &s->config.cols);
-    qemu_put_be16s(f, &s->config.rows);
-
-    qemu_put_be32s(f, &s->config.max_nr_ports);
+    /* The config space (ignored on the far end in current versions) */
+    get_config(vdev, (uint8_t *)&config);
+    qemu_put_be16s(f, &config.cols);
+    qemu_put_be16s(f, &config.rows);
+    qemu_put_be32s(f, &config.max_nr_ports);
 
     /* The ports map */
     max_nr_ports = s->serial.max_virtserial_ports;
@@ -987,8 +988,6 @@
         vser->ovqs[i] = virtio_add_queue(vdev, 128, handle_output);
     }
 
-    vser->config.max_nr_ports =
-        virtio_tswap32(vdev, vser->serial.max_virtserial_ports);
     vser->ports_map = g_malloc0(((vser->serial.max_virtserial_ports + 31) / 32)
         * sizeof(vser->ports_map[0]));
     /*

include/hw/virtio/virtio-serial.h

diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
index a679e54..11af978 100644
--- a/include/hw/virtio/virtio-serial.h
+++ b/include/hw/virtio/virtio-serial.h
@@ -207,8 +207,6 @@
     /* bitmap for identifying active ports */
     uint32_t *ports_map;
 
-    struct virtio_console_config config;
-
     struct VirtIOSerialPostLoad *post_load;
 
     virtio_serial_conf serial;