[Xen-devel] Bugs with block devices to domU - let's find solution

[Guryanov Dmitry <dimak@xxxxxxxxxxxx>]

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

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