hw/i386/pc: Allow instantiating a virtio-iommu device

hw/i386/pc: Allow instantiating a virtio-iommu device

Allow instantiating a virtio-iommu device by adding an ACPI Virtual I/O
Translation table (VIOT), which describes the relation between the
virtio-iommu and the endpoints it manages.

Add a hotplug handler for virtio-iommu on x86 and set the necessary
reserved region property. On x86, the [0xfee00000, 0xfeefffff] DMA
region is reserved for MSIs. DMA transactions to this range either
trigger IRQ remapping in the IOMMU or bypasses IOMMU translation.

Although virtio-iommu does not support IRQ remapping it must be informed
of the reserved region so that it can forward DMA transactions targeting
this region.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-Id: <20211026182024.2642038-5-jean-philippe@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>