[PATCH 0/4] intel_iommu: Reset vIOMMU after all the rest of devices

[peterx]

From: Peter Xu <peterx@redhat.com>

There're issue reported that when syetem_reset the VM with an intel iommu
device and MT2892 PF(mlx5_core driver), the host kernel throws DMAR error.

  https://issues.redhat.com/browse/RHEL-7188

Alex quickly spot a possible issue on ordering of device resets.

It's verified by our QE team then that it is indeed the root cause of the
problem.  Consider when vIOMMU is reset before a VFIO device in a system
reset: the device can be doing DMAs even if the vIOMMU is gone; in this
specific context it means the shadow mapping can already be completely
destroyed.  Host will see these DMAs as malicious and report.

To fix it, we'll need to make sure all devices under the vIOMMU device
hierachy will be reset before the vIOMMU itself.  There's plenty of trick
inside, one can get those by reading the last patch.

I didn't check other vIOMMUs, but this series should fix the issue for VT-d
as of now.  The solution can be slightly ugly, but a beautiful one can be
very non-trivial.

Review comments welcomed, thanks.

Peter Xu (4):
  reset: qemu_register_reset_one()
  reset: Allow multiple stages of system resets
  intel_iommu: Tear down address spaces before IOMMU reset
  intel_iommu: Reset vIOMMU at the last stage of system reset

 include/sysemu/reset.h |  5 ++++
 hw/core/reset.c        | 67 ++++++++++++++++++++++++++++++------------
 hw/i386/intel_iommu.c  | 56 +++++++++++++++++++++++++++++++++--
 3 files changed, 107 insertions(+), 21 deletions(-)

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2.43.0