[Qemu-devel] Communication between Windows 7 host and Linux guest

[Qemu-devel] Communication between Windows 7 host and Linux guest

[Gripon Sébastien]

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Hi,

I have the need to communicate efficiently between Windows 7 host and linux guest. I tried first to use an IP socket communication using TAP driver on Windows. Unfortunately, we reach a maximum of 4 Mbits/s where I would need faster communication (more than 10 Mb/s). I don’t know yet if the TAP driver is slow.

Anyway, I wonder if there are other way to do such communication. In the qemu reference help, I can see that there are some options to communicate through a pipe for example:

-chardev backend ,id=id [,mux=on|off] [,options]
Backend is one of: null, socket, udp, msmouse, vc, ringbuf, file, pipe, console, serial, pty, stdio, braille, tty, parallel, parport, spicevmc. spiceport. The specific backend will determine the applicable options.

But I don’t really understand what this exactly does and I never managed to use it. Is it supposed to map some hardware read/write on read/write on pipe? What kind of hardware? How to use it? Do I need modifications on the Linux guest?

Thanks a lot for your help,

sgripon

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Re: [Qemu-devel] Communication between Windows 7 host and Linux guest

[Stefan Hajnoczi]

On Sun, Dec 22, 2013 at 07:15:18PM +0000, Gripon Sébastien wrote:
> I have the need to communicate efficiently between Windows 7 host and linux guest. I tried first to use an IP socket communication using TAP driver on Windows. Unfortunately, we reach a maximum of 4 Mbits/s where I would need faster communication (more than 10 Mb/s). I don’t know yet if the TAP driver is slow.

That seems very slow, 100 Mbit/s should definitely be achievable.  But I
have never tried TAP on Windows.

Can you share the QEMU command-line and the benchmark used to measure
this result?

Stefan

Re: [Qemu-devel] Communication between Windows 7 host and Linux guest

[Gripon Sébastien]

This is the command line:

qemu-system-armw -M versatilepb -kernel ..\BaseQemu\zImage -hda ..\BaseQemu\rootfs.squashfs -hdb ..\BaseQemu\flash.ext3 -append "root=/dev/sda r" -net tap,ifname=TAP,script=no -net nic 

I talked with the developer here and it seems that the bad speed is mainly due to latency. We are investigating also on our side because we use a "special" environment: in fact, we use VisualGDB to debug from Visual studio into qemu. It seems that VisualGDB's ssh client has poor performances but I don't know yet where the latency come from.

Sebastien

-----Message d'origine-----
De : Stefan Hajnoczi [mailto:stefanha@gmail.com] 
Envoyé : lundi 6 janvier 2014 03:15
À : Gripon Sébastien
Cc : qemu-devel@nongnu.org
Objet : Re: [Qemu-devel] Communication between Windows 7 host and Linux guest

On Sun, Dec 22, 2013 at 07:15:18PM +0000, Gripon Sébastien wrote:
> I have the need to communicate efficiently between Windows 7 host and linux guest. I tried first to use an IP socket communication using TAP driver on Windows. Unfortunately, we reach a maximum of 4 Mbits/s where I would need faster communication (more than 10 Mb/s). I don’t know yet if the TAP driver is slow.

That seems very slow, 100 Mbit/s should definitely be achievable.  But I have never tried TAP on Windows.

Can you share the QEMU command-line and the benchmark used to measure this result?

Stefan