Xen Dom0 5.0_STABLE and shared disks

[Juraj Hercek <nbsd%hck.sk@localhost>]

Hello,

I've been using domU domains with shared disks in read only mode with 
the 5.99.X dom0 kernels. Now, I've switched to stable branch and I 
figured out I cannot do this anymore with 5.0_STABLE dom0 kernel.

This is what I used to use in domU config files:

domU_1:
...
disk = [ 'phy:/dev/wd0g,0x01,w',
         'phy:/dev/wd0f,0x02,r' ]
...

domU_2:
...
disk = [ 'phy:/dev/wd0h,0x01,w',
         'phy:/dev/wd0f,0x02,r' ]
...

This doesn't work anymore. When starting domU_2, xenback complains about 
failing VOP_OPEN with errno 16 (EBUSY). When wd0f was mounted in dom0, 
even domU_1 failed with the same/similar error.

Is there any workaround besides exporting disks via NFS (resp. iSCSI)? 
I'd like to avoid networked solution (NFS, iSCSI) in order to save some 
CPU ticks spent on ip stack code.

Thanks,
Juraj