vtd: Increase DRHD_MAX_UNITS

[erj]

Summary

Observed on a couple Ice Lake-SP platforms (Intel Coyote Pass, Dell
R750), there are more than 8 DRHD sections enumerated in the DMAR ACPI
section. Since the previous limit was 8, this resulted in some of these
not being parsed by vtd when the iommu is initialized; in this case when
PCI devices are being passthru'd to a bhyve VM.

This omission later causes a kernel panic later in initialization when
devices could not be found in a valid DRHD scope because the DHRD
containing the device's scope was not added to vtd.

Signed-off-by: Eric Joyner <[e-mail]>

PR: 268486
Sponsored by: Intel Corporation

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I could not find anything on what a max limit on the number of DRHDs could be in the VT-d spec 4.0; should the drhds and vtdmaps arrays be turned into arbitrary-length linked lists instead?

[rew]

I don't see any issues with this offhand - be nice to have this fixed for 13.2

[jhb]

It would be nice to make these dynamically sized rather than a fixed-sized array. However, reviewing and integrating @kib's patch to use the ACPI_DMAR driver for this instead is probably the better long-term fix.

[erj]

In D38285#871102, @jhb wrote:

It would be nice to make these dynamically sized rather than a fixed-sized array. However, reviewing and integrating @kib's patch to use the ACPI_DMAR driver for this instead is probably the better long-term fix.

Is D25672 what you're referring to/related to it?

[kib]

In D38285#871126, @erj wrote:

In D38285#871102, @jhb wrote:

It would be nice to make these dynamically sized rather than a fixed-sized array. However, reviewing and integrating @kib's patch to use the ACPI_DMAR driver for this instead is probably the better long-term fix.

Is D25672 what you're referring to/related to it?

Yes, it is. It is old and require a work just to revive it. To get it into a committable state, much more work is needed. Also we do not have ACPI driver for AMD IOMMU.