[RFC v2] tag IOMMU-protected devices in dom0 fdt

[Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>]

At the moment, dom0 can't distinguish which devices are protected by
IOMMU and which are not. In some cases, this can cause swiotlb bounce
buffer use for DMA addresses above 32 bits, which in turn can lead
to poor performance.

Previous discussions at [1,2] agreed upon passing info about IOMMU via
device tree. This series does that in a way consistent with existing iommu 
bindings.

[1] 
https://lore.kernel.org/all/1392913234-25429-1-git-send-email-julien.grall__16109.9684810781$1392913341$gmane$org@xxxxxxxxxx/
[2] https://lore.kernel.org/all/cover.1633106362.git.roman_skakun@xxxxxxxx/

Sergiy Kibrik (2):
  xen/arm: introduce dummy iommu node for dom0
  arm/xen: don't use xen DMA ops when the device is protected

Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: Roman Skakun <rm.skakun@xxxxxxxxx>
Cc: Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>
Cc: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
Cc: Andrii Anisov <Andrii_Anisov@xxxxxxxx>
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2.25.1