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Re: [Qemu-discuss] Virtioconsole problem

From: Dunrong Huang
Subject: Re: [Qemu-discuss] Virtioconsole problem
Date: Sun, 21 Oct 2012 00:52:16 +0800


2012/10/20 Eviatar Khen <address@hidden>:
> Thanks a lot for your help!
> I am not sure regarding the command line, as I took it from the page. The
> intension was to open two consoles (hvc0 and hvc1), one for terminal and one
> for remote gdb debug.
> It is important to me to use the virtio-serial (multiport) as I need to
> understand its mechanism.
> If I understand correctly the right command is:
> ./x86_64-softmmu/qemu-system-x86_64 -no-acpi -m 500 fedora17.img -device
> virtio-serial -chardev socket,path=/tmp/foo,server,nowait,id=foo -chardev
> socket,path=/tmp/bar,server,nowait,id=bar -device
> virtconsole,chardev=foo,name=org.fedoraproject.console.foo -device
> virtconsole,chardev=bar,name=org.fedoraproject.console.foo
That is not what I mean.
Actually, -chardev and -device you passed to QEMU are a combination, we can
call them backend and frontend:
1.) -chardev. Host can open the backend of chardev to communicate with
     the guest. e.g. if chardev backend is a socket, host app can open
it to communicate
     with guest. We can call it backend.

2.) -device. QEMU will expose a device to guest so guest can open it
for communication
     with host. The device's full path guset will see is depended on
device's name. In your case,
     guest will see a device, whose full path is
     We can call it frontend.

So, you create two virtio console devices for guest, but they have the
same name. This means
guest can only see a device on /dev/virtio-ports, is this what you really need?

> Does "virtconsole" opens virtio device?
See above, it is guest's responsibilities for opening the device. QEMU
just expose virtio
device to guest.
> Thanks again for this great help.
> Eviatar
> On 10/20/2012 01:15 PM, Dunrong Huang wrote:
>> Hi,
>> 2012/10/20 Eviatar Khen <address@hidden>:
>>> Hello all,
>>> On a linux machine I'm preforming the following command (with a binary
>>> compiled from latest release):
>>> ./x86_64-softmmu/qemu-system-x86_64 -no-acpi -m 500 fedora17.img -device
>>> virtio-serial -chardev socket,path=/tmp/foo,server,nowait,id=foo -chardev
>>> socket,path=/tmp/bar,server,nowait,id=bar -device
>>> virtioconsole,chardev=foo,name=org.fedoraproject.console.foo -device
>>> virtioconsole,chardev=bar,name=org.fedoraproject.console.foo
>> Why did you use same name for different virtconsole name?
>>> And I'm getting the following error:
>>> qemu-system-x86_64: -device
>>> virtioconsole,chardev=foo,name=org.fedoraproject.console.foo: Parameter
>>> 'driver' expects device type
>> virtioconsole has been deprecated, please use -device virtconsole or
>> -device virtio-serial
>> instead.
>>> I'm new to qemu, could someone help me with this.
>>> What am I doing wrong? What this error means? I took the line from:
>>> http://fedoraproject.org/wiki/Features/VirtioSerial#How_To_Test
>> The wiki is too old, it should be updated based on new QEMU code.
>>> Thank you and best regards,
>>> Eviatar

Best Regards,

Dunrong Huang

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