Hi Peter, On 12/10/2017 11:54, Peter Maydell wrote: > On 11 October 2017 at 17:08, Auger Eric <eric.au...@redhat.com> wrote: >> Hi Peter, >> >> On 11/10/2017 16:56, Peter Maydell wrote: >>> On 19 September 2017 at 08:46, Eric Auger <eric.au...@redhat.com> wrote: >>>> This series implements the virtio-iommu device. >>>> >>>> This v4 is an upgrade to v0.4 spec [1] and applies on QEMU v2.10.0. >>>> - probe request support although no reserved region is returned at >>>> the moment >>>> - unmap semantics less strict, as specified in v0.4 >>>> - device registration, attach/detach revisited >>>> - split into smaller patches to ease review >>>> - propose a way to inform the IOMMU mr about the page_size_mask >>>> of underlying HW IOMMU, if any >>>> - remove warning associated with the translation of the MSI doorbell >>>> >>>> The device gets instantiated using the "-device virtio-iommu-device" >>>> option. It currently works with ARM virt machine only, as the machine >>>> must handle the dt binding between the virtio-mmio "iommu" node and >>>> the PCI host bridge node. >>> >>> Could this work on x86, or is it inherently arm-only? >> >> Yes this is the goal. At the moment the ACPI probing is not yet properly >> specified but a Q35 prototype was developed in the Red Hat Virt team. >> This will be presented at the KVM forum. > > Since I have very little familiarity with virtio or iommu code, > I'd be much happier if this was reviewed as a generic virtio-iommu > by the x86/virtio devs and then the arm specific parts done second...
Understood. I was rather expecting you to review the smmuv3 emulation code which you did, in a comprehensive manner ;-), and many thanks for that. Note sure this is time yet to get this RFC reviewed as - the v0.4 virtio-iommu driver it relies on was not officially submitted, - the virtio-iommu specification review has not really been reviewed, - the ACPI probing method has not been discussed yet. Jean-Philippe, please correct me if I am wrong. So to me, this is pure RFC at the moment. > > I'm also not clear on what we're expecting the recommended or normal > way to do device passthrough is going to be -- this virtio-mmio, > or presenting the guest with an SMMUv3 interface? Do we really > need to implement both ? I think the KVM forum is the right place to sync as both approaches will be presented and some pros/cons + performance figures will be given. As we talk about choosing, there is one alternative that was suggested on the ML by Alex & Michael but never really get considered yet and maybe should be: using intel iommu emulation code for ARM. I aknowledge this deserves a thorough impact study on kernel and FW side but I would be happy to get your opinion about the QEMU side. Would you have a by- principle rejection of this idea to instantiate such an Intel device in mach virt or would it be something you would be ready to consider? Thanks Eric > > thanks > -- PMM >
