Bugs with block devices to domU - let's find solution

Bugs with block devices to domU - let's find solution

[Guryanov Dmitry]

Hello

I have the same bug, that've been disscussed before - domU can't find 
any block devices and crashes with "Unable to mount root fs". I've spend 
a week under heavy debugging and find, that this bug take place because 
dom0 backend driver can't read parameter physical-device from xenstore. 
For example /local/domain/0/backend/vbd/1/776/physical_device, where  1- 
domU id, 776=0x308 - major and minor numbers of block device, which will 
used by domU.
This parameter must be written by script /etc/xen/scripts/block, which 
must start like /etc/xen/scripts/vif-bridge any time as domU starts, but 
it doesn't.

So, there is a question to xen developers: when and how must this script 
must been started ?


P.S.
To start domU i comment out block in backend driver, where this 
parameter must be obtained and give explicitly value for that variable:

file -    linux-.../drivers/xen/blkback/xenbus.c
function - backend_changed

replace
---------------------
    err = xenbus_scanf(NULL, dev->nodename,
               "physical-device", "%li", &pdev);
   
    if (XENBUS_EXIST_ERR(err))
        return;
---------------------

with, for example:
---------------------
pdev=0x307;   //hda7 - physical device
err=1;
---------------------


--
Guryanov Dmitry

Re: Bugs with block devices to domU - let's find solution

[Stephan Boni]

> Hello
> 
> I have the same bug, that've been disscussed before - domU can't find 
> any block devices and crashes with "Unable to mount root fs". 
> I've spend 
> a week under heavy debugging and find, that this bug take 
> place because 
> dom0 backend driver can't read parameter physical-device from 
> xenstore. 
> For example 
> /local/domain/0/backend/vbd/1/776/physical_device, where  1- 
> domU id, 776=0x308 - major and minor numbers of block device, 
> which will 
> used by domU.
> This parameter must be written by script 
> /etc/xen/scripts/block, which 
> must start like /etc/xen/scripts/vif-bridge any time as domU 
> starts, but 
> it doesn't.
> 
> So, there is a question to xen developers: when and how must 
> this script 
> must been started ?

I have this problem too! Can anyone of the xen developers solve this problem? It seams, it's the last very critical bug we have.

Thanks a lot.

Stephan

Re: Bugs with block devices to domU - let's find solution

[Ewan Mellor]

On Tue, Oct 18, 2005 at 09:06:51PM +0400, Guryanov Dmitry wrote:

> Hello
> 
> I have the same bug, that've been disscussed before - domU can't find 
> any block devices and crashes with "Unable to mount root fs". I've spend 
> a week under heavy debugging and find, that this bug take place because 
> dom0 backend driver can't read parameter physical-device from xenstore. 
> For example /local/domain/0/backend/vbd/1/776/physical_device, where  1- 
> domU id, 776=0x308 - major and minor numbers of block device, which will 
> used by domU.
> This parameter must be written by script /etc/xen/scripts/block, which 
> must start like /etc/xen/scripts/vif-bridge any time as domU starts, but 
> it doesn't.
> 
> So, there is a question to xen developers: when and how must this script 
> must been started ?

This script is run by your hotplug / udev installation inside dom0 when the
domU starts up.  Do you have hotplug and udev installed in dom0?

Ewan.

Re: Bugs with block devices to domU - let's find solution

[Guryanov Dmitry]

Ewan Mellor wrote:

>On Tue, Oct 18, 2005 at 09:06:51PM +0400, Guryanov Dmitry wrote:
>
>  
>
>>Hello
>>
>>I have the same bug, that've been disscussed before - domU can't find 
>>any block devices and crashes with "Unable to mount root fs". I've spend 
>>a week under heavy debugging and find, that this bug take place because 
>>dom0 backend driver can't read parameter physical-device from xenstore. 
>>For example /local/domain/0/backend/vbd/1/776/physical_device, where  1- 
>>domU id, 776=0x308 - major and minor numbers of block device, which will 
>>used by domU.
>>This parameter must be written by script /etc/xen/scripts/block, which 
>>must start like /etc/xen/scripts/vif-bridge any time as domU starts, but 
>>it doesn't.
>>
>>So, there is a question to xen developers: when and how must this script 
>>must been started ?
>>    
>>
>
>This script is run by your hotplug / udev installation inside dom0 when the
>domU starts up.  Do you have hotplug and udev installed in dom0?
>
>  
>
>Ewan.
>
>  
>
Thanks, that's was a bug, now it works properly.

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