[vfio-users] No IOMMU Groups seen in /sys/kernel/iommu_groups/

[Alex Williamson]

On Fri, 22 Nov 2019 15:07:30 +0530
Venumadhav Josyula <vjosyula at gmail.com> wrote:

> Hi All,
> We are trying to use vfio-pci. We have following
> - intel_iommu=on in bios
> - it shows in /proc/cmdline
> 
> [root at vflac2-kvm ~]# cat /proc/cmdline
> BOOT_IMAGE=/vmlinuz-3.10.0-957.1.3.el7.x86_64 root=/dev/mapper/c7--kvm-root
> ro crashkernel=auto rd.lvm.lv=c7-kvm/root rd.lvm.lv=c7-kvm/swap rhgb
> quiet *intel_iommu=on
> *isolcpus=2,3,6,7
> [root at vflac2-kvm ~]# dmesg | grep IOM
> *[    0.000000] DMAR: IOMMU enabled*

As explained in [1] this only indicates the processing of the
intel_iommu=on command line option.  Full dmesg might be required to
understand the issue.

> [root at vflac2-kvm ~]# uname -mrs
> Linux 3.10.0-957.1.3.el7.x86_64 x86_64
> [root at vflac2-kvm ~]# ls /sys/kernel/iommu_groups/
> 
> *[root at vflac2-kvm ~]# ls -al /sys/kernel/iommu_groups/total 0*
> 
> 
> 
> 04:00.0 Ethernet controller: Intel Corporation Ethernet Controller
> 10-Gigabit X540-AT2 (rev 01)
> 04:00.1 Ethernet controller: Intel Corporation Ethernet Controller
> 10-Gigabit X540-AT2 (rev 01)
> 04:10.0 Ethernet controller: Intel Corporation X540 Ethernet Controller
> Virtual Function (rev 01)
> 04:10.2 Ethernet controller: Intel Corporation X540 Ethernet Controller
> Virtual Function (rev 01)
> 05:00.0 Ethernet controller: Intel Corporation Ethernet Controller X710 for
> 10GbE SFP+ (rev 02)
> 05:00.1 Ethernet controller: Intel Corporation Ethernet Controller X710 for
> 10GbE SFP+ (rev 02)
> 
> Can u suggest what could wrong ? We  are seeing no iommu_groups getting
> created.

What's the CPU model?  There are some that don't have IOMMU support.
Thanks,

Alex

[1]http://vfio.blogspot.com/2016/09/intel-iommu-enabled-it-doesnt-mean-what.html