This commit converts the virtio-console device to create a new
virtio-serial bus that can host console and generic serial ports. The
file hosting this code is now called virtio-serial-bus.c.

The virtio console is now a very simple qdev device that sits on the
virtio-serial-bus and communicates between the bus and qemu's chardevs.

This commit also includes a few changes to the virtio backing code for
pci and s390 to spawn the virtio-serial bus.

As a result of the qdev conversion, we get rid of a lot of legacy code.
The old-style way of instantiating a virtio console using

    -virtioconsole ...

is maintained, but the new, preferred way is to use

    -device virtio-serial -device virtconsole,chardev=...

With this commit, multiple devices as well as multiple ports with a
single device can be supported.

For multiple ports support, each port gets an IO vq pair. Since the
guest needs to know in advance how many vqs a particular device will
need, we have to set this number as a property of the virtio-serial
device and also as a config option.

In addition, we also spawn a pair of control IO vqs. This is an internal
channel meant for guest-host communication for things like port
open/close, sending port properties over to the guest, etc.

This commit is a part of a series of other commits to get the full
implementation of multiport support. Future commits will add other
support as well as ride on the savevm version that we bump up here.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Add feature bits as properties to virtio. This makes it possible to e.g. define
machine without indirect buffer support, which is required for 0.10
compatibility, or without hardware checksum support, which is required for 0.11
compatibility.  Since default values for optional features are now set by qdev,
get_features callback has been modified: it sets non-optional bits, and clears
bits not supported by host.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Rename features->guest_features. This is
what they are, avoid confusion with
host features which we also need to keep around.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Currently we always set the "config space changed" bit to 1 when triggering
any virtio interrupt. While that worked in 2.6.27, newer kernels interpret
that value as "only the config space changed and nothing else happened".

Since we usually trigger interrupts to tell the guest that something did
happen, we just not tell it the config space changed for now until we
implement the correct callback for that.
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

On S390x we don't want to go through the hassle of emulating real existing
hardware, because we don't need to for running Linux.

So let's instead implement a machine that is 100% based on VirtIO which we
fortunately implement already.

This patch implements the bus that is the groundwork for such an S390x
virtio machine.
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>