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     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
     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.


     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 <>.