The MSI doorbell on Apple HW can be any address in the low 4GB range.
However, the MSI write is matched by the PCIe block before hitting the
iommu. It must thus be excluded from the IOVA range that is assigned to any
PCIe device.

Link: https://lore.kernel.org/r/20210929163847.2807812-9-maz@kernel.orgTested-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sven Peter <sven@svenpeter.dev>