[PATCH v5 1/2] iommu: introduce domain attribute for nesting IOMMUs

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

Some IOMMUs, such as the ARM SMMU, support two stages of translation.
The idea behind such a scheme is to allow a guest operating system to
use the IOMMU for DMA mappings in the first stage of translation, with
the hypervisor then installing mappings in the second stage to provide
isolation of the DMA to the physical range assigned to that virtual
machine.

In order to allow IOMMU domains to be used for second-stage translation,
this patch adds a new iommu_attr (IOMMU_ATTR_NESTING) for setting
second-stage domains prior to device attach. The attribute can also be
queried to see if a domain is actually making use of nesting.

Cc: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Acked-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Signed-off-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
---
 include/linux/iommu.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 20f9a527922a..7b02bcc85b9e 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -80,6 +80,7 @@ enum iommu_attr {
 	DOMAIN_ATTR_FSL_PAMU_STASH,
 	DOMAIN_ATTR_FSL_PAMU_ENABLE,
 	DOMAIN_ATTR_FSL_PAMUV1,
+	DOMAIN_ATTR_NESTING,	/* two stages of translation */
 	DOMAIN_ATTR_MAX,
 };
 
-- 
2.1.0