NAME
vmd – Intel Volume Management Device driver
SYNOPSIS
device vmd
In loader.conf(5): hw.vmd.bypass_msi hw.vmd.max_msi hw.vmd.max_msix vmd_load="YES"
DESCRIPTION
This driver attaches to Intel VMD devices, representing them as PCI-to-PCI bridges and providing access to children PCI devices via new PCI domains. Intel VMD is used by Intel's VROC (Virtual RAID on chip) to manage NVMe drives.
LOADER TUNABLES
The following tunables are settable via loader(8) or sysctl(8):
- hw.vmd.bypass_msi
-
By default all VMD devices remap children MSI/MSI-X interrupts into their own. It creates additional isolation, but also complicates things due to sharing, etc. Fortunately some VMD devices can bypass the remapping. Defaults to 1.
- hw.vmd.max_msi
-
Limits number of Message Signaled Interrupt (MSI) vectors allowed to each child device. VMD can't distinguish MSI vectors of the same device, so there are no benefits to have more than one, unless it is required by specific device driver. Defaults to 1.
- hw.vmd.max_msix
-
Limits number of Extended Message Signaled Interrupt (MSI-X) vectors allowed to each child device. VMD has limited number of interrupt vectors to map children interrupts into, so to avoid/reduce sharing children devices/drivers need to be constrained. Defaults to 3.
SEE ALSO
HISTORY
The vmd driver first appeared in FreeBSD 13.0.