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35 .Nd Intel Volume Management Device driver
37 To compile this driver into the kernel, place the following lines in your
38 kernel configuration file:
39 .Bd -ragged -offset -indent
43 Alternatively, to load the driver as a module at boot time, place the following
46 .Bd -literal -offset indent
50 This driver attaches to Intel VMD devices, representing them as PCI-to-PCI
51 bridges and providing access to children PCI devices via new PCI domains.
52 Intel VMD is used by Intel's VROC (Virtual RAID on chip) to manage NVMe
55 The following tunables are settable via
59 .Bl -tag -width indent
60 .It Va hw.vmd.bypass_msi
61 By default all VMD devices remap children MSI/MSI-X interrupts into their
62 own. It creates additional isolation, but also complicates things due to
63 sharing, etc. Fortunately some VMD devices can bypass the remapping.
66 Limits number of Message Signaled Interrupt (MSI) vectors allowed to each
68 VMD can't distinguish MSI vectors of the same device, so there are no
69 benefits to have more than one, unless it is required by specific device
72 .It Va hw.vmd.max_msix
73 Limits number of Extended Message Signaled Interrupt (MSI-X) vectors
74 allowed to each child device.
75 VMD has limited number of interrupt vectors to map children interrupts into,
76 so to avoid/reduce sharing children devices/drivers need to be constrained.
84 driver first appeared in