On 07/07/2017 16:21, Pavel Butsykin wrote:
We should guarantee that RAM will not be modified while VM has a stopped
state, otherwise it can lead to negative consequences during post-copy
migration. In RUN_STATE_FINISH_MIGRATE step, it's expected that RAM on
source side will not be modified as this could lead to non-consistent vm state
on the destination side. Also RAM access during postcopy-ram migration with
enabled release-ram capability can lead to sad consequences.
Let's add enable_backend() callback to avoid undesirable virtioqueue changes
in the guest memory.
Signed-off-by: Pavel Butsykin <address@hidden>
---
hw/char/virtio-console.c | 21 +++++++++++++++++++++
hw/char/virtio-serial-bus.c | 7 +++++++
include/hw/virtio/virtio-serial.h | 3 +++
3 files changed, 31 insertions(+)
diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c
index 0cb1668c8a..b55905892e 100644
--- a/hw/char/virtio-console.c
+++ b/hw/char/virtio-console.c
@@ -163,6 +163,26 @@ static void chr_event(void *opaque, int event)
}
}
+static void virtconsole_enable_backend(VirtIOSerialPort *port, bool enable)
+{
+ VirtConsole *vcon = VIRTIO_CONSOLE(port);
+
+ if (!qemu_chr_fe_get_driver(&vcon->chr)) {
+ return;
+ }
+
+ if (enable) {
+ VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
+
+ qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
+ k->is_console ? NULL : chr_event,
+ vcon, NULL, false);
+ } else {
+ qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL,
+ NULL, NULL, NULL, false);
+ }
+}
I think you can also factorize the code in virtconsole_realize() to call
this new function.
static void virtconsole_realize(DeviceState *dev, Error **errp)
{
VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
@@ -233,6 +253,7 @@ static void virtserialport_class_init(ObjectClass *klass,
void *data)
k->unrealize = virtconsole_unrealize;
k->have_data = flush_buf;
k->set_guest_connected = set_guest_connected;
+ k->enable_backend = virtconsole_enable_backend;
Why don't you register a vm_state change handler to change the state of
the virtconsole according to the state of the machine instead of adding
a new function in the VirtIOSerialPortClass?
See a23a6d1 ("virtio-rng: stop virtqueue while the CPU is stopped")