Re: PV networking issue in 2.6.38.6 and 2.6.39-rc7 pvops dom0 kernels

[Mario <mario@slackverse.org>]

On 05/17/2011 01:04 PM, Pasi Kärkkäinen wrote:
> On Tue, May 17, 2011 at 12:49:18PM +0200, Mario wrote:
>> On 05/16/2011 03:22 PM, Pasi Kärkkäinen wrote:
>>> On Mon, May 16, 2011 at 03:15:53PM +0200, Mario wrote:
>>>> On 05/16/2011 03:09 PM, Mario wrote:
>>>>> On 05/16/2011 03:06 PM, Ian Campbell wrote:
>>>>>> On Mon, 2011-05-16 at 14:04 +0100, Mario wrote:
>>>>>>> So you are telling me that 2.6.38 does not have a working networking on
>>>>>>> PV guests, but HVM does?
>>>>>>
>>>>>> Yes, netback did not go upstream until 2.6.39 so PV networking (either
>>>>>> for PV or HVM guests with PV drivers) will not work on mainline kernels
>>>>>> before that.
>>>>>>
>>>>>> Emulated HVM networking does not use netback so that will work on
>>>>>> earlier kernels (it depends on qemu)
>>>>>>
>>>>>> Ian.
>>>>>>
>>>>>
>>>>> Ok, thanks, it all makes more sense now. :-)
>>>>
>>>>
>>>> Ian, while i have your attention, any idea why some framebuffer devices
>>>> blank screen when dom0 boots up. I have seen this happen mostly on older
>>>> vga cards but its not a rule. Should i just keep on blacklisting kernel
>>>> modules for those cards, or is there some kind of a more general
>>>> solution?
>>>
>>> You could try "nomodeset" parameter to disable KMS modesetting..
>>> (and possibly adding "console=tty0")
>>>
>>> Xen patches for DRM/KMS haven't been merged to upstream Linux yet.
>>>
>>> -- Pasi
>>>
>>
>>
>> nomodeset and/or nofb do not seem to help.
>> console=tty0 also does not seem to have any effect.
>>
>> Only way to successfuly boot dom0 is with one of these:
>>
>> CONFIG_FB=n
>>
>> or
>>
>> echo "blacklist s3fb">  /etc/modprobe.d/blacklist-s3fb.conf
>>
>> As soon as fb device is modprobed, booting stops, and server freezes.
>> Can anything else be done? Perhaps some setting for xen in kernel..?
>
> Set up a serial console and configure Xen + dom0 kernel log to it..
> and see what goes wrong. http://wiki.xen.org/xenwiki/XenSerialConsole
>
> ie. does dom0 kernel crash while loading s3fb?
>
> -- Pasi
>


Well, i forgot to mention one more method, that is to add: fbcon=map:X
Where X is something that is not in /proc/fb, basicly an invalid device.
So, for example: fbcon=map:9

To make it short, dom0 freezes/crashes and it never reaches a full 
booted up state, so it will not respond to pings. The last thing 
displayed on the screen is s3fb being loaded and that /dev/fb0 was created.

When i first experienced this problem, it was back when i first tried 
Xen 4.0.1, however, i had just a blank screen with blinking cursor to 
work with. So i had to set up a serial console to figure out what was 
wrong. After seeing how it stops on framebuffer, i blacklisted the 
module, and it worked. I kept on doing so on every other setup i have 
made, but now, one year later, i was wondering if this is ever going to 
be fixed, or if i can somehow help to get it fixed.. :-)


m.