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Re: [vfio-users] Strange behavior with recent update. ACS(?) & VFIO



On 08/02/2016 04:22 PM, Mark wrote:
After the update, pulse audio no longer reports audio devices in the
host.  Trying to figure out why this is, I've removed all passthrough
devices from all VMs in virt-manager, removed the vfio module load
options, but vfio_pci still claims the 3 devices.  The only way I've
been able to get the audio devices back is to BLACKLIST the vfio module.

Did you regenerate your initramfs?

My questions are:

1. Is there any other way besides /etc/modules.d/vfio.conf that vfio
could be told to claim a device on boot?

vfio-pci.ids=8086:1234 on the kernel command line (cat /proc/cmdline)

2. Is ACS impacting my ability to have the host use a device claimed by
iommu because of a recent change?

ACS only affects the separation (or grouping) of devices into IOMMU groups. It does not impact your ability to use devices on the host. The IOMMU does not "claim" devices. Unless you set iommu=pt, even the host goes through the IOMMU for all hardware access.

3. Is there another way of going about assigning a claimed device to the
host?

echo 8086:0a0c > /sys/bus/pci/drivers/snd_hda_intel/new_id

4. Can I no longer only assign 2 of 3 devices in an iommu group to vfio?

It is not safe to split an IOMMU group between two guests, or the host and a guest.

Thank you


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