From 55289fb036481396466d7825fa01d829c891108c Mon Sep 17 00:00:00 2001
From: Pavel Butsykin
Date: Tue, 19 Sep 2017 15:07:33 +0300
Subject: virtio-serial: add enable_backend callback

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 <pbutsykin@virtuozzo.com>
Message-Id: <20170919120733.22020-1-pbutsykin@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/char/virtio-serial-bus.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'hw/char/virtio-serial-bus.c')

diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 17a1bb008a..9470bd7be7 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -637,6 +637,13 @@ static void set_status(VirtIODevice *vdev, uint8_t status)
     if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
         guest_reset(vser);
     }
+
+    QTAILQ_FOREACH(port, &vser->ports, next) {
+        VirtIOSerialPortClass *vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
+        if (vsc->enable_backend) {
+            vsc->enable_backend(port, vdev->vm_running);
+        }
+    }
 }
 
 static void vser_reset(VirtIODevice *vdev)
-- 
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