From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
Subject: Re: IXGBE, IOMMU DMAR DRHD handling fault issue
Date: Thu, 1 Feb 2018 10:10:14 +0000
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To: Ravi Kerur <rkerur@gmail.com>
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On 31-Jan-18 9:51 PM, Ravi Kerur wrote:
> 
> Hi Anatoly,
> 
> Thanks. I am following wiki link below which uses vIOMMU with DPDK as a 
> use-case and instantiate VM as specified with Q35 chipset in Qemu.
> 
> https://wiki.qemu.org/Features/VT-d
> 
> Qemu-version is 2.11
> Host kernel 4.9
> Guest kernel 4.4
> 
> I can only guess that guest kernel needs an upgrade in my setup to work 
> correctly, if versions on my setup rings a bell on not having support 
> kindly let me know.
> 
> When 'modprobe vfio enable_unsafe_noiommu_node=Y' is executed on guest I 
> get following error
> ...
> vfio: unknown parameter 'enable_unsafe_noiommu_node' ignored
> ...
> 
> in guest.
> 
> Thanks.

AFAIK kernel 4.4 should have noiommu mode - it was introduced in 3.1x 
days. However, in order for that to work, kernel also has to be built 
with this mode enabled. My guess is, whoever is the supplier of your 
kernel, did not do that. You should double-check the kernel 
configuration of your distribution.

However, if you have vIOMMU in QEMU, you shouldn't need noiommu mode - 
"regular" vfio should work fine. noiommu mode should only be needed if 
you know you don't have IOMMU enabled in your kernel, and even if you 
can't enable it, you can still use igb_uio.

-- 
Thanks,
Anatoly