Comment 3 for bug 917135

Can we get the drivers included in the initramfs? Without having them loaded, Ubuntu running on Hyper-V will be forced to install using the older non-PV drivers (for IDE) and not have access to SCSI or network unless specifically configured.

Additionally, as ata_piix is statically linked in Ubuntu 12.04, we are unable to control our root device with our hv_storvsc driver. On other distributions, we use modprobe rules to block the loading of ata_piix. As I see it, we have two options:

1. Build Hyper-V relevant storage driver as part of the kernel and we can fix the initialization ordering to ensure that our PV drivers control the root device when Ubuntu is running on a Hyper-V host. When not running on a Hyper-V host, our drivers will not successfully initialize and so will not have any effect. This would simultaneously address your need for fast boot while also addressing the performance issues on the root device when hosted on Hyper-V.
2. Modify the ata driver to recognize that when hosted on Hyper-V, it should not control the disks.

Let me know if either of those are options we can collaborate on.