FreeBSD manual
download PDF document: vmd.4.pdf
VMD(4) FreeBSD Kernel Interfaces Manual VMD(4)
NAME
vmd - Intel Volume Management Device driver
SYNOPSIS
To compile this driver into the kernel, place the following lines in your
kernel configuration file:
device vmd
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
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
graid(8)
HISTORY
The vmd driver first appeared in FreeBSD 13.0.
FreeBSD 14.2-RELEASE October 6, 2022 FreeBSD 14.2-RELEASE