Using virtual IOMMU in guest hypervisors other than KVM and Xen?

[Jintack Lim]

Hi,

I'm trying to pass through a physical network device to a nested VM
using virtual IOMMU. While I was able to do it successfully using KVM
and Xen guest hypervisors running in a VM respectively, I couldn't do
it with Hyper-V as I described below. I wonder if anyone have
successfully used virtual IOMMU in other hypervisors other than KVM
and Xen? (like Hyper-V or VMware)

The issue I have with Hyper-V is that Hyper-V gives an error that the
underlying hardware is not capable of doing passthrough. The exact
error message is as follows.

Windows Power-shell > (Get-VMHost).IovSupportReasons
The chipset on the system does not do DMA remapping, without which
SR-IOV cannot be supported.

I'm pretty sure that Hyper-V recognizes virtual IOMMU, though; I have
enabled iommu in windows boot loader[1], and I see differences when
booing a Windows VM with and without virtual IOMMU. I also checked
that virtual IOMMU traces are printed.

I have tried multiple KVM/QEMU versions including the latest ones
(kernel v5.3, QEMU 4.1.0) as well as two different Windows servers
(2016 and 2019), but I see the same result. [4]

I'd love to hear if somebody is using virtual IOMMU in Hyper-V or
VMware successfully, especially for passthrough. I also appreciate if
somebody can point out any configuration errors I have.

Here's the qemu command line I use, basically from the QEMU vt-d
page[2] and Hyper-v on KVM from kvmforum [3].

./qemu/x86_64-softmmu/qemu-system-x86_64 -device
intel-iommu,intremap=on,caching-mode=on -smp 6 -m 24G -M
q35,accel=kvm,kernel-irqchip=split -cpu
host,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time -drive
if=none,file=/vm/guest0.img,id=vda,cache=none,format=raw -device
virtio-blk-pci,drive=vda --nographic -qmp
unix:/var/run/qmp,server,nowait -serial
telnet:127.0.0.1:4444,server,nowait -netdev
user,id=net0,hostfwd=tcp::2222-:22 -device
virtio-net-pci,netdev=net0,mac=de:ad:be:ef:f2:12 -netdev
tap,id=net1,vhost=on,helper=/srv/vm/qemu/qemu-bridge-helper -device
virtio-net-pci,netdev=net1,disable-modern=off,disable-legacy=on,mac=de:ad:be:ef:f2:11
-device vfio-pci,host=0000:06:10.0,id=net2 -monitor stdio -usb -device
usb-tablet -rtc base=localtime,clock=host -vnc 127.0.0.1:4 --cdrom
win19.iso --drive file=virtio-win.iso,index=3,media=cdrom

Thanks,
Jintack

[1] 
https://social.technet.microsoft.com/Forums/en-US/a7c2940a-af32-4dab-8b31-7a605e8cf075/a-hypervisor-feature-is-not-available-to-the-user?forum=WinServerPreview
[2] https://wiki.qemu.org/Features/VT-d
[3] https://www.linux-kvm.org/images/6/6a/HyperV-KVM.pdf
[4] https://www.mail-archive.com/address@hidden/msg568963.html