-----Original Message-----
From: Olaf Hering [mailto:olaf@aepfle.de]
Sent: Tuesday, August 30, 2011 8:49 AM
To: KY Srinivasan
Cc: gregkh@suse.de; linux-kernel@vger.kernel.org;
devel@linuxdriverproject.org; virtualization@lists.osdl.org
Subject: Re: [PATCH 0000/0046] Staging: hv: Driver cleanup

On Sat, Aug 27, K. Y. Srinivasan wrote:

quoted

	2) Handle all block devices using the storvsc driver. I have modified
	   the implementation here based on Christoph's feedback on my earlier
	   implementation.

The upgrade path from hv_blkvsc to hv_storvsc is difficult.

hv_storvsc does not provide the vmbus:hv_block modalias, so mkinitrd
does not know what module to choose when mkinitrd is called in a
previous kernel (like sles11sp1).


In a guest with both SCSI and IDE controllers the IDE disks are
discovered first, so the SCSI drives will also change their names.
Thats not a problem for data partitions because they could be mounted by
UUID or LABEL in fstab.
But its difficult to adjust /boot/grub/device.map for example because
the old  IDE drives do not provide an identifier. What is the best way
to make sure the rename from hd* to sd* in such config files is done
correctly? Is it safe to assume that all drives with a class_id of
32412632-86cb-44a2-9b5c50d1417354f5 are connected to IDE ports?

The class_id is invariant as we are returning the guid of the device under class_id.

So, if you see a IDE guid under class_id, you can be sure (a) it is an ide device and (b)
it is a device managed via the PV drivers.

localhost:~ # head /sys/bus/vmbus/devices/vmbus_0_{1,2,3,10,11}/class_id
==> /sys/bus/vmbus/devices/vmbus_0_1/class_id <==
{32412632-86cb-44a2-9b5c50d1417354f5}

==> /sys/bus/vmbus/devices/vmbus_0_2/class_id <==
{32412632-86cb-44a2-9b5c50d1417354f5}

==> /sys/bus/vmbus/devices/vmbus_0_3/class_id <==
{32412632-86cb-44a2-9b5c50d1417354f5}

==> /sys/bus/vmbus/devices/vmbus_0_10/class_id <==
{ba6163d9-04a1-4d29-b60572e2ffb1dc7f}

==> /sys/bus/vmbus/devices/vmbus_0_11/class_id <==
{ba6163d9-04a1-4d29-b60572e2ffb1dc7f}


In my test system, the IDE drives are now discovered twice, once by
hv_storvsc and once by libata:

This is a known (old problem). The way this was handled earlier was to have the 
modprobe rules in place to setup a dependency that would force the load of the
hyper-v driver (blk / stor) ahead of the native driver and if the load of the PV
driver succeeded, we would not load the native driver. In sles11 sp1, we had a rule for 
loading blkvsc. With the merge of blkvsc and storvsc, the only change we need to make
is to have storvsc in the rule (instaed of blkvsc).

Regards,

K. Y