Comment 19 for bug 942316

Mike Sterling (mike-sterling) wrote on 2012-03-05:
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After reviewing this - I suspect the issue is the modifications to ata_piix to prevent it from loading on a Hyper-V platform. Since ata_piix now detects a Hyper-V platform and unloads if it's found, this would prevent the OS from installing. We need a modification to the patch here ( VVM: only for history :-) . . ./lp929545-precise/0001-ata_piix-defer-to-the-Hyper-V-drivers-by-default.patch ) that will only unload the block device handling, not the CD/DVD device handling.
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 Done: 1) in Ubuntu kernel already 2) for "vanila kernel" send patch ( Big thanks Andy Whitcroft (apw)! ) see
http://marc.info/?l=linux-kernel&m=133304222215301&w=2
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List: linux-kernel
Subject: [PATCH 1/1] ata_piix: defer disks to the Hyper-V paravirtualised drivers by default
From: Andy Whitcroft <apw () canonical ! com>
Date: 2012-03-29 17:28:50

When we are hosted on a Hyper-V hypervisor the guest disks are exposed
both via the Hyper-V paravirtualised drivers and via an emulated SATA disk
controller. We want to use the paravirtualised drivers where possible as
they are much more performant. The Hyper-V paravirtualised drivers only
expose the virtual hard disk devices, the CDROM/DVD devices must still
be enumerated on the virtualised SATA controller. As we have no control
over kernel probe order for these two drivers especially when one driver
is builtin to the kernel and the other a module, we need to prevent the
ata_piix driver from claiming the disks devices by default when running
on a Hyper-V hypervisor.

When enumerating the drives look at the aquired device ID and if it
appears to be a disk device then report it as disconnected. Limit this
behaviour to when we have detected a Hyper-V hypervisor. Finally allow
this behaviour to be overriden via a new module parameter.

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