Re: [PATCH v5 04/12] hw/i386/pc: Allow instantiating a virtio-iommu device

[Jean-Philippe Brucker]

On Thu, Oct 21, 2021 at 03:47:09PM +0200, Igor Mammedov wrote:
> On Wed, 20 Oct 2021 18:27:38 +0100
> Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:
> 
> > 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.
> 
> shouldn't above be "IO remapping"?

No it is IRQ remapping: DMA writes to this address range are interrupt
requests and the IOMMU may either perform interrupt remapping or pass it
to the APIC directly

> 
> > 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>
> > Tested-by: Eric Auger <eric.auger@redhat.com>
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> 
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>

Thanks!
Jean