Failure to shutdown/reboot with intel_iommu=on

[Uwe Kleine-König]

Hello,

On my Lenovo T460p I cannot shutdown and reboot when the iommu is
enabled. This is using linux 5.2.7 as provided by Debian, 5.6.4 has the
same problem. Suspend/resume also fails; I suspect this is the same
issue.

When requesting power off the kernel messages just end with:

	sd 0:0:0:0: [sda] Synchronizing SCSI cache
	sd 0:0:0:0: [sda] Stopping disk
	e1000e: EEE TX LPI TIMER: 00000011
	ACPI: Preparing to enter system sleep state S5
	reboot: Power down
	acpi_power_off called

(photo at https://www.kleine-koenig.org/tmp/uklsiommu.jpg in case I
mistyped something. Full dmesg and lspci -vvv at
https://www.kleine-koenig.org/tmp/uklsiommu.tar.gz with and without
iommu enabled.)

With the iommu disabled (CONFIG_INTEL_IOMMU_DEFAULT_ON unset or
intel_iommu=off on cmdline) the machine just works as expected
(including working suspend/resume).

I already talked to tglx on irc but unfortunately no new insights
resulted from that.

Any ideas how to fix or continue debugging the issue?

Best regards
Uwe

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