Differential D7666

Leave ppt devices in the host domain when they are not attached to a VM.
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Authored by jhb on Aug 26 2016, 9:01 PM.

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Reviewers

grehan

Commits

rS305485: Leave ppt devices in the host domain when they are not attached to a VM.

Summary

Leave ppt devices in the host domain when they are not attached to a VM.

This allows a pass through device to be reset to a normal device driver
on the host and reused on the host. ppt devices are now always active in
some I/O MMU domain when the I/O MMU is active, either the host domain
or the domain of a VM they are attached to.

Test Plan

start a VM using device pass through and verify via dmardump that the device moves back to domain 1 after the VM shuts down. (Previously it just disappeared from the dump since the entry was disabled.)

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Unit

No Test Coverage

Build Status

Buildable 5002
Build 5069: arc lint + arc unit

Event Timeline

jhb updated this revision to Diff 19740.Aug 26 2016, 9:01 PM

jhb retitled this revision from to Move ppt devices back to the host domain when a VM shuts down..

jhb updated this object.

jhb edited the test plan for this revision. (Show Details)

jhb added a reviewer: grehan.

Herald added a subscriber: imp. · View Herald TranscriptAug 26 2016, 9:01 PM

FYI, I have moved this out to the ppt driver due to other changes I have in flight. Will update once I have tested the new version, but you can ignore this for now until I upload the next version.

Place all PCI devices in the host domain during initialization.
Change ppt to move devices into the host domain instead of removing them.
Remove device before adding it to the host domain.
Remove device from host domain before adding it to the VM domain.

jhb retitled this revision from Move ppt devices back to the host domain when a VM shuts down. to Leave ppt devices in the host domain when they are not attached to a VM..Aug 27 2016, 12:41 AM

jhb updated this object.

Another approach perhaps would be to fix iommu_add_device() to permit "moving" a device between domains. I think this mostly just means removing the explicit panic from vtd_add_device() (though perhaps there are other gotchas there I am not aware of?). If we go that route, I would remove the calls to iommu_remove_device() from ppt.c.

jhb added a reviewer: PCI.Aug 29 2016, 8:00 PM

jhb removed a reviewer: PCI.Aug 29 2016, 8:16 PM