linux-kernel - Re: [PATCH 0000/0046] Staging: hv: Driver cleanup

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Date:	Tue, 30 Aug 2011 10:43:30 -0700
From:	Greg KH <greg@...ah.com>
To:	KY Srinivasan <kys@...rosoft.com>
Cc:	Olaf Hering <olaf@...fle.de>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>
Subject: Re: [PATCH 0000/0046] Staging: hv: Driver cleanup

On Tue, Aug 30, 2011 at 05:22:54PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Olaf Hering [mailto:olaf@...fle.de]
> > Sent: Tuesday, August 30, 2011 8:49 AM
> > To: KY Srinivasan
> > Cc: gregkh@...e.de; linux-kernel@...r.kernel.org;
> > devel@...uxdriverproject.org; virtualization@...ts.osdl.org
> > Subject: Re: [PATCH 0000/0046] Staging: hv: Driver cleanup
> > 
> > On Sat, Aug 27, K. Y. Srinivasan wrote:
> > 
> > > 	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).

Why do we need a rule at all?  Shouldn't the module dependancy stuff
handle the autoloading of the drivers properly from the initrd now that
the hotplug logic is hooked up properly?

What am I missing here?

Or is the hotplug code not working correctly?

greg k-h
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