Problem with the serial port in Fedora Core 6 -xen kernel

[Jim Cornette]

Gene Heskett wrote:
> On Saturday 11 November 2006 19:42, Craig White wrote:
>
>> ----
>> you're detective work notwithstanding, Bill Nottingham's suggestion to
>> put an entry into 'udev' rules was the suggested recommendation for the
>> problem but since you didn't try that with the xen kernel, didn't post
>> your results on this bugzilla entry after trying the recommended entry,
>> I guess none of us will ever be certain.

Someone with the Xen kernel version should be able to repeat this 
without any problem. It sounds like virtual devices are being created 
but real devices are not, such as serial ports.

> 
> And what sort of an entry might that be?  It does create 4 devices now, as 
> its written to do, but the devices are worthless when the onboard 
> hardware hasn't been detected.

Since xen is a category on the installer if you choose to install 
virtualization, many other people have installed the xen kernel and were 
caught with real hardware problems. Devices effected on my hearing were 
video problems, lockups and now serial communication ports.

> 
>> I guess I am glad that the non-xen kernel gives you what you wanted
>> after all (the serial port interfaces for your X11). I just assumed that
>> you chose the xen kernel with the intent to run xen virtualization, but
>> I am guessing that your motherboard doesn't support xen which is
>> probably the cause of the problem in the first place.

Isn't XEN restrained to a file, has no hardware unless setup to use real 
hardware? I am not sure about xen and machine capability but I know that 
my laptop with sufficient memory would stay railed at full speed and 
would not last very long with this condition. Also, on other computers 
the system memory is so low that xen would not work properly.
It sounds like the problem that happened to Gene and others is even 
thinking that the xen version of the kernel would interfere with the 
operation of their computer. The thought of users was probably that they 
would try out virtualization at a later date. No user would suspect 
problems until they tried to setup virtualization,

> 
> Either way (I didn't choose it, anaconda did), and I have NDI if this 
> biostar mobo supports xen or not, there has been precious little 
> discussions about it on the  50+ mailing lists I lurk on.

I believe memory requirements are 256 MB per domain that you setup. I 
cannot recall if it is a requirement for a GUI virtual system or text 
based systems. I have not used xen myself. I used vmware before but 
believe they are with different goals and regard the hardware differently.

>> Now I agree with you that getting rid of the xen kernel solves this
>> problem. I don't agree with you a bit that it wasn't a udev problem
>> because if you again read Comment #5 on the above referenced bugzilla
>> entry, it is obvious that Bill Nottingham believes it is a udev related
>> problem.
> 
> I still don't see what, if anything, udev could do about it when the 
> hardware has not been detected.  Does it have some sort of a magic 
> twanger for that case that we common mortals don't know about?  I'm now 
> looking at that #5 comment, but have no clue because theres no preamble 
> describing where to put those commands, which I assume would go 
> in /.etc/udev/rules.d/50-udev.rules, but it contains no similar rules.  
> Those in the know will I assume know where in that file, but to me thats 
> not a usable fix without the whole story.  But with some use of a 
> figurative shovel to dig a little deeper it seems to indicate it should 
> be added into /etc/udev/rules.d/05-udev-early-rules.  It would be more at 
> home there by far.
> 
> Is this correct?
> 

Don't know but one would think that serial devices like com ports were 
recognized and initialized by the common standards for serial ports.

> There is a second reason I didn't pursue that angle, any attempt to 
> modprobe anything 8250 related failed due to undefined labels in the 
> module(s).  Which brings me back to square one, what can udev  do about 
> it when the kernel can't find the hardware in the first place?  Heck, 
> right now, with them running, an lspci -vv doesn't show them.  Whether 
> they should show I don't recall.  I just checked on my firewall box, and 
> they don't appear there either, so perhaps I'm using the wrong tool.

When one installs virtualization, the kernel for xen should not be the 
default kernel. A normal kernel should also be installed and set to default.

> 
> Sorry I'm so dense in your opinion.  If it will make you feel better, I'll 
> plead oldtimers since I had a birthday last month, having made it to 72.

Your age is in close proximity to my parents and both seem to have their 
faculties still. Happy belated BD.

Jim

> 
>> Craig
> 


-- 
I have a theory that it's impossible to prove anything, but I can't 
prove it.