We keep port 0 reserved for compat with older guests, where only
virtio-console was expected. Even if a system is started without a
virtio-console port, port #0 is kept aside. However, after a
virtconsole port is unplugged, port id 0 became available, and the next
hotplug of a virtserialport caused failure due to it not being a console
port.
Steps to reproduce:
$ ./x86_64-softmmu/qemu-system-x86_64 -m 512 -cpu host -enable-kvm -device
virtio-serial-pci -monitor stdio -vnc :1
QEMU 2.0.91 monitor - type 'help' for more information
(qemu) device_add virtconsole,id=p1
(qemu) device_del p1
(qemu) device_add virtserialport,id=p1
Port number 0 on virtio-serial devices reserved for virtconsole devices for
backward compatibility.
Device 'virtserialport' could not be initialized
(qemu) quit
Reported-by: dengmin <md...@redhat.com>
Signed-off-by: Amit Shah <amit.s...@redhat.com>
---
v2:
- move calculation of 'i' inside if stmt too (Paolo)
- re-word comment
---
hw/char/virtio-serial-bus.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 07bebc0..917e93e 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -797,10 +797,18 @@ static void add_port(VirtIOSerial *vser, uint32_t port_id)
static void remove_port(VirtIOSerial *vser, uint32_t port_id)
{
VirtIOSerialPort *port;
- unsigned int i;
- i = port_id / 32;
- vser->ports_map[i] &= ~(1U << (port_id % 32));
+ /*
+ * Don't mark port 0 removed -- we explicitly reserve it for
+ * backward compat with older guests, ensure a virtconsole device
+ * unplug virtconsole retains the reservation.
+ */
+ if (port_id) {
+ unsigned int i;
+
+ i = port_id / 32;
+ vser->ports_map[i] &= ~(1U << (port_id % 32));
+ }
port = find_port_by_id(vser, port_id);
/*
--
1.9.3
