Re: [Xen-users] Need to Access 2 Serial Ports in HVM Win 2K3 server.

[Trolle Selander <trolle.selander@xxxxxxxxx>]

You did send to the list as well - I just forgot to press "reply to all" rather than reply in gmail. :)
Anyway, I haven't looked into this for a long time, but I know there were issues with serial ports when recieving, and though I'm not completely positive exactly what is going on, my guess is an interrupt latency issue - the time between the FIFO threshold interrupt happening and the serial driver actually processing the interrupt may be too long, allowing the FIFO to overfill and characters to be lost. If your 8 port serial card has modern enough UARTs to support hardware flow control, you could try turning that on to see if it makes a difference. I had some success in improving this situation by dedicating one cpu strictly to dom0. Also, the improved serial emulation in qemu-dm in Xen versions from 3.2 and newer also helps some.

-- Trolle

On Tue, May 12, 2009 at 9:52 PM, David Griswold <david.griswold@xxxxxxxxx> wrote:

Sorry - I thought I had sent my last reply to the list as well.

 

Thanks for the advice, that is exactly what I did, and it worked, in that I could see and access to serial ports in the Win2k3 domU.  Unfortunately, I think I am going to have to scrap this configuration.  I am running Hylafax in the dom0 and serial port performance under the xen kernel is not acceptable.  I can't even reliable receive one fax at a time let alone have all 8 ports on the 8 port fax modem active at once.  When I boot into the native kernel, I have no issues at all.  I would have expected this had I been running hylafax in a domU, but not the dom0.

 

Have you seen performance issues in regards to serial ports?

 

David

-----Original Message-----
From: Trolle Selander [mailto:trolle.selander@xxxxxxxxx]
Sent: Tuesday, May 12, 2009 4:59 PM
To: David Griswold
Subject: Re: [Xen-users] Need to Access 2 Serial Ports in HVM Win 2K3 server.

You could let the config file create com1 and let the wrapper script only add com2.

-- Trolle

On Tue, May 12, 2009 at 5:52 PM, David Griswold <david.griswold@xxxxxxxxx> wrote:

I had a brain fart when I created the qemu.2serial script - forgot to
put the '#! /bin/bash' at the top of it.

Since, I have upgraded to xen 3.3.1 from the the gitco repo.  I am
still having issues.  It seems that by default qemu-dm will provide
more emulated hardware, like a serial and parallel port, unless you
tell it not to (serial none).  When I have attempted to configure the
.sxp file with more than one serial port, the vm won't start.  If I
use the wrapper script, then I get a 'com1' and 'com2' in the device
manager, but com1 doesn't work and in fact hyperterminal sees two
'com1' ports.  I am sure this is a confusion between the default
serial port provided to the vm and the serial ports I am trying to
give to it via the wrapper script.

So, I succeeded in starting a hvm where windows sees two serial ports,
but one of them doesn't work.

David

On Mon, May 11, 2009 at 3:35 PM, David Griswold

<david.griswold@xxxxxxxxx> wrote:

> Ok, so I saved the attached script to /usr/lib/xen/bin/qemu.2serial,
> chmod  to 755 and added this to the domU config file:
>
> device_model = "/usr/lib/xen/bin/qemu-dm.2serial"
>
> and removed the 'serial =' entries from the config.  I started the vm
> and I get the same results as before with the vm listed but not
> running.  There doesn't appear to be anything more in the logs.
>
> David
>

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