[Bug 684875] Re: Patch to Natty 2.6.37-virtual breaks non-EC2 users

[Alex Bligh]

xen-devel thread is here:
  http://www.gossamer-threads.com/lists/xen/devel/192003

I've been asked to point out there are really two problems:

1. If the emulated devices (i.e. the "real" sda) is not unplugged, there
is a device name clash. The emulated devices cannot be unplugged on xen
3.3 (because it doesn't support it), but unless you pass
unplug=unnecessary, it won't actually allow the PV drivers, so you lose
PV support. On 3.4 and onwards you might pass unplug=unnecessary anyway
to get consistent device mapping with xen 2.6.18 supplied kernel, in
which case you will get the device name clash.

2. Even if the unplugging works, you then get inconsistent device
mapping, because both mainline, 2.6.18 and everything else expect to see
virtual devices under /dev/xvda, not /dev/sda, so although you won't get
the clash (i.e. the failure to register the device), the device will
have an unexpected name which can and will break stuff.

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https://bugs.launchpad.net/bugs/684875

Title:
  Patch to Natty 2.6.37-virtual breaks non-EC2 users