Larry Finger [off-list ref] writes:

On 09/21/2017 06:37 AM, Zwindl wrote:

quoted

Hi, I've reported to archlinux's bugzilla, and finally found out the
flag which caused that issue, it's the
`CONFIG_INTEL_IOMMU_DEFAULT_ON=y` flag, I think may this is a kernel
bug, more details at https://bugs.archlinux.org/task/55665

My standard kernel has the following:

CONFIG_INTEL_IOMMU=y
# CONFIG_INTEL_IOMMU_SVM is not set
# CONFIG_INTEL_IOMMU_DEFAULT_ON is not set

I will do some further testing to see if turning
CONFIG_INTEL_IOMMU_DEFAULT_ON also breaks my system.

But not all systems have iommu so check from dmesg that iommu is really
enabled.

-- 
Kalle Valo