Re: [Qemu-devel] Virtual IOMMU + Virtio-net devices in a Windows VM doesn't work

[Yan Vugenfirer]

> On 26 Jul 2018, at 05:53, Jintack Lim <address@hidden> wrote:
> 
> Hi Peter,
> 
> On Tue, Jul 24, 2018 at 1:55 AM Peter Xu <address@hidden> wrote:
>> 
>> On Mon, Jul 23, 2018 at 04:13:18PM -0400, Jintack Lim wrote:
>>> Hi,
>>> 
>>> I'm running a Windows VM on top of KVM on x86, and one of virtio-net
Hi,

What Windows OS are you using? Keep in mind that IOMMU support in Windows 
drivers will work in Windows 10 and Windows Server 2016.
What’s the version of the virtio-win drivers are you using (should be build 150 
and up, or to include the following commit: 
https://github.com/virtio-win/kvm-guest-drivers-windows/commit/eac3270d10924903ff38a08fcdaa252604d2e4a9)?

Best regards,
Yan.

>>> device in the Windows VM doesn't seem to work. I provided virtual
>>> IOMMU and two virtio-net devices to the VM: one bypassing the virtual
>>> IOMMU and the other one behind the virtual IOMMU[1]. It turned out
>>> that the virtio-net device behind virtual IOMMU didn't work while the
>>> one bypassing the virtual IOMMU worked well. In a linux VM with the
>>> same configuration, both of virtio-net device worked well.
>>> 
>>> I found that there is a subtle difference between virtio-net devices
>>> bypassing and behind virtual IOMMU in a Linux VM. The lscpu command in
>>> the Linux VM shows different device names for them; the first line is
>>> for the bypassing one, and the second line is for the one behind the
>>> virtual IOMMU
>>> 
>>> 00:03.0 Ethernet controller: Red Hat, Inc Virtio network device
>>> 01:00.0 Ethernet controller: Red Hat, Inc Device 1041 (rev 01)
>>> 
>>> I wonder if this difference somehow caused the problem in the Windows
>>> VM. I've installed the latest virtio drivers (0.1.149) from the fedora
>>> project [2]
>>> 
>>> Any thoughts?
>>> 
>>> I'm using v4.15 Linux kernel as a host, and QEMU 2.11.0.
>> 
>> Have you tried the latest QEMU?
>> 
> 
> I just tried the latest QEMU, but observed the same symptom.
> 
>> Also CC Jason and Michael.
> 
> Thanks!
> 
>> 
>>> 
>>> Thanks,
>>> Jintack
>>> 
>>> [1] https://wiki.qemu.org/Features/VT-d
>>> [2] 
>>> https://docs.fedoraproject.org/quick-docs/en-US/creating-windows-virtual-machines-using-virtio-drivers.html
>>> 
>>> 
>> 
>> Regards,
>> 
>> --
>> Peter Xu
>> 
> 
>