Re: [Xen-users] PV networking issue in 2.6.38.6 and 2.6.39-rc7 pvops dom0 kernels

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, May 17, 2011 at 01:20:32PM +0200, Mario wrote:
> 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.. :-)
>

Yep, you can help by posting the full boot logs from serial console, 
both Xen and dom0 linux kernel logs.

http://wiki.xen.org/xenwiki/XenSerialConsole

and: http://wiki.xensource.com/xenwiki/XenParavirtOps, 
especially the "Are there more debugging options .." section.

-- Pasi


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