From: Jean-Philippe Brucker <redacted>
Sent: Wednesday, October 13, 2021 8:11 PM

Support identity domains, allowing to only enable IOMMU protection for a
subset of endpoints (those assigned to userspace, for example). Users
may enable identity domains at compile time
(CONFIG_IOMMU_DEFAULT_PASSTHROUGH), boot time
(iommu.passthrough=1) or
runtime (/sys/kernel/iommu_groups/*/type = identity).

Patches 1-2 support identity domains using the optional
VIRTIO_IOMMU_F_BYPASS_CONFIG feature. The feature bit is not yet in the
spec, see [1] for the latest proposal.

Patches 3-5 add a fallback to identity mappings, when the feature is not
supported.

Note that this series doesn't touch the global bypass bit added by
VIRTIO_IOMMU_F_BYPASS_CONFIG. All endpoints managed by the IOMMU
should
be attached to a domain, so global bypass isn't in use after endpoints
are probed. Before that, the global bypass policy is decided by the
hypervisor and firmware. So I don't think Linux needs to touch the
global bypass bit, but there are some patches available on my
virtio-iommu/bypass branch [2] to test it.

QEMU patches are on my virtio-iommu/bypass branch [3] (and the list)

[1] https://www.mail-archive.com/virtio-dev@lists.oasis-
open.org/msg07898.html
[2] https://jpbrucker.net/git/linux/log/?h=virtio-iommu/bypass
[3] https://jpbrucker.net/git/qemu/log/?h=virtio-iommu/bypass

Jean-Philippe Brucker (5):
  iommu/virtio: Add definitions for VIRTIO_IOMMU_F_BYPASS_CONFIG
  iommu/virtio: Support bypass domains
  iommu/virtio: Sort reserved regions
  iommu/virtio: Pass end address to viommu_add_mapping()
  iommu/virtio: Support identity-mapped domains

 include/uapi/linux/virtio_iommu.h |   8 ++-
 drivers/iommu/virtio-iommu.c      | 113 +++++++++++++++++++++++++-----
 2 files changed, 101 insertions(+), 20 deletions(-)

For this series:

	Reviewed-by: Kevin Tian [off-list ref]
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