HV_ATA_PCI_DISENGAGE(4FREEBSD) - man page online | special files

Hyper-V ATA PCI Disengage driver.

September 10, 2013
HYPER-V(4)                         BSD Kernel Interfaces Manual                        HYPER-V(4)


hv_ata_pci_disengage — Hyper-V ATA PCI Disengage driver


To compile this driver into the kernel, place the following lines in the system kernel con‐ figuration 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.


hv_vmbus(4), hv_utils(4), hv_netvsc(4), hv_storvsc(4)


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 <>.
BSD September 10, 2013 BSD
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hv_ata_pci_disengage(4freebsd) referred by hv_kvp(4freebsd) | hv_netvsc(4freebsd) | hv_storvsc(4freebsd) | hv_utils(4freebsd) | hv_vmbus(4freebsd)
refer to hv_netvsc(4freebsd) | hv_storvsc(4freebsd) | hv_utils(4freebsd) | hv_vmbus(4freebsd)