Created attachment 848228 [details]
SEGV stacktrace from syslog

On my Dell XPS 15 9560, when running with kernel cmdline options
  acpi_rev_override=1 intel_iommu=on,igfx_off mitigations=auto
the new 5.3.18-lp152.69-default causes a SEGV in intel-iommu:
  kernel BUG at ../drivers/iommu/intel-iommu.c:1389
This prevents (among other things) my wifi from working (Qualcomm Atheros
QCA6174 802.11ac). I've attached the relevant part of the syslog.

Disabling intel_iommu, by running with
  acpi_rev_override=1 intel_iommu=off,igfx_off mitigations=auto
prevents the SEGV (as expected since it disables the iommu).

The previous kernel, 5.3.18-lp152.66-default, still works fine with the
now-broken intel_iommu=on setting.