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Rework pass through changes in r305485 to be safer.

Description

Rework pass through changes in r305485 to be safer.

Specifically, devices that do not support PCI-e FLR and were not
gracefully shutdown by the guest OS could continue to issue DMA
requests after the VM was terminated. The changes in r305485 meant
that those DMA requests were completed against the host's memory which
could result in random memory corruption. Instead, leave ppt devices
that are not attached to a VM disabled in the IOMMU and only restore
the devices to the host domain if the ppt(4) driver is detached from a
device.

As an added safety belt, disable busmastering for a pass-through device
when before adding it to the host domain during ppt(4) detach.

PR: 222937
Tested by: Harry Schmalzbauer <freebsd@omnilan.de>
Reviewed by: grehan
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D12661

Details

Committed
jhbOct 27 2017, 2:57 PM
Reviewer
grehan
Differential Revision
D12661: Rework pass through changes in r305485 to be safer.
Parents
rS325038: MFC r324804:
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