Re: [Xen-devel] [Xen-users] Multiple serial ports in Windows HVM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-07-28 at 16:41 +0000, White, Edmund H wrote:
> > On Fri, 2014-07-25 at 17:40 +0000, White, Edmund H wrote:
> > > > Subject: Re: [Xen-users] Multiple serial ports in Windows HVM
> > > >
> > > > On Thu, 2014-07-24 at 20:08 +0000, White, Edmund H wrote:
> > > > > I have just moved from Xen 4.3 to 4.4. With 4.3 I used the xm
> > > > > toolstack, and
> > > > I could define multiple serial ports in the config for my Windows
> > > > domU like
> > > > so:
> > > > >
> > > > > serial = [ "tcp::4464,server,nowait",
> > > > > "file:/home/ed/logs/Tgt64bcom2.log" ]
> > > >
> > > > I had no idea xm would accept a list here. We should probably look
> > > > at extending libxl/xl to support that. Is that something you think
> > > > you could take a look at?
> > > >
> > >
> > > I have literally no idea where to start, but if you give me some pointers 
> > > I'll
> > take a look.
> > 
> > You would need to add a new field to libxl_domain_build_info.u.hvm in
> > tools/libxl/libxl_types.idl e.g. serial_list and add a LIBXL_HAVE #define to
> > libxl.h to signal the presence of this new field.
> > 
> > Then plumb it into tools/libxl/libxl_dm
> > libxl__build_device_model_args_*.
> > 
> > Lastly update xl_cmdimpl.c:parse_config_data to spot the use of a list
> > instead of a simple string and populate the new field (+ docs updates etc).
> > 
> > George Dunlap did something very similar for the usb option in these two
> > commits:
> > 
> > c3a214819270 xl: Accept a list for usbdevice in config file
> > ac16730d0339 libxl: Allow multiple USB devices on HVM domain creation
> > 
> > I think you can pretty much just file off the usb and write serial in its 
> > place ;-)
> > 
> > See http://wiki.xen.org/wiki/Submitting_Xen_Patches for more general
> > advice on the patch workflow etc.
> > 
> 
> OK. I will look into it.

Super, thanks!

> One question: should the end result be that you can use a single item OR a 
> list,
> or a list only? In other words, should [] be optional or mandatory?

We need to support the old syntax for compat with old users, so [] needs
to be optional please.

> > > I had tried that without success before posting to the list. I tried
> > > again today and now have it working. The successful recipe is to define 
> > > the
> > first serial port with:
> > >
> > > serial = "tcp::4464,server,nowait"
> > >
> > > and the second with
> > >
> > > device_model_args = [ "-serial", "file:/home/ed/logs/Tgt64bcom2.log" ]
> > 
> > Interesting. I'd have expected:
> >         device_model_args = [ "-serial", "tcp::4464,server,nowait",
> >                               "-serial", 
> > "file:/home/ed/logs/Tgt64bcom2.log" ] by itself to
> > also work equally well.
> > 
> 
> It may have done, but I was concerned that if I didn't define the first 
> serial port through 'serial =' there
> would be some default that I didn't want.
> 
> My original attempts were failing because I was placing "-serial value" in a 
> single string (as both the docs and
> your original reply imply), and that results in something that looks correct 
> but which qemu can't parse properly.

Oops, sorry. Do you have any suggestions for a change which would have
made the docs at least not so confusing?

Ian.


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