kern/166174: [xen] Problems ROOT MOUNT ERROR < freebsd 8.3>

[Bill Cole]

The following reply was made to PR kern/166174; it has been noted by GNATS.

From: "Bill Cole" <fbsdbugs-20120604 at billmail.scconsult.com>
To: bug-followup at FreeBSD.org, ilsujang at gmail.com
Cc:  
Subject: Re: kern/166174: [xen] Problems ROOT MOUNT ERROR &lt;freebsd 8.3&gt;
Date: Mon, 04 Jun 2012 16:29:08 -0400

 This problem remains in 8.3-RELEASE and in the current RELENG_8_3. A 
 kernel built for amd64 with the XENHVM config on 8.2p4 boots properly 
 under XenServer 5.6 or 6.0, but the same config with 8.3 fails to detect 
 and attach the xbd0 device for the root filesystem. The 8.3 GENERIC 
 kernel boots normally as well, but without the Xen PV drivers.
 
 I have tried to get a XENHVM kernel working both by updating a 8.2p4 
 XENHVM system to RELENG_8_3 with its existing config and by installing a 
 fresh 8.3-RELEASE/GENERIC system on a new VM and building XENHVM kernels 
 on it: in all cases the failure is identical. I was able to update the 
 8.3-RELEASE/GENERIC system to a RELENG_8_3/GENERIC kernel and world from 
 source without any trouble. I am reasonably experienced with 
 custom-built kernel installs & I'm pretty sure that I've gone back over 
 every "stupid sysadmin" failure mode and eliminated it. Device driver 
 code is a realm for younger brains, but I am suspicious that the root 
 cause is somewhere in the extensive changes made to 
 src/sys/dev/xen/blkfront/blkfront.c and connected code ahead of the 8.3 
 release.