HYPER-V(4) FreeBSD Kernel Interfaces Manual HYPER-V(4)


hv_ata_pci_disengageHyper-V ATA PCI Disengage driver


To compile this driver into the kernel, place the following lines in the system kernel configuration file:

device hyperv


The hv_ata_pci_disengage driver prevents the native FreeBSD ATA driver from loading in the presence of Hyper-V. FreeBSD guests running on Hyper-V can take advantage of the Hyper-V Storage Virtual Consumer ( hv_storvsc(4)) for using their IDE devices. Since the ATA driver serves IDE devices as well, there is a chance that the ATA driver may interfere with the operations of hv_storvsc(4). The hv_ata_pci_disengage driver avoids conflicts between the ATA driver and hv_storvsc(4) by disabling the ATA driver when the FreeBSD guest is booting.

A side effect of disabling the ATA driver is that CDROM may become inoperational on FreeBSD guest partitions. If CDROM access is a must then users may use "set hw.ata.disk_enable=1" at boot time to prevent the ATA driver from being disabled.


Support for hv_ata_pci_disengage first appeared in FreeBSD 10.0. The driver was developed through a joint effort between Citrix Incorporated, Microsoft Corporation, and Network Appliance Incorporated.


FreeBSD support for hv_ata_pci_disengage was first added by Microsoft BSD Integration Services Team <bsdic@microsoft.com>.
September 10, 2013 FreeBSD