On 21/02/18 22:59, Jordan Crouse wrote:
Add a new domain attribute to enable the TTBR1 pagetable for drivers
and devices that support it.  This will enabled using a TTBR1 (otherwise
known as a "global" or "system" pagetable for devices that support a split
pagetable scheme for switching pagetables quickly and safely.

TTBR1 is very much an Arm VMSA-specific term; if the concept of a split address space is useful in general, is it worth trying to frame it in general terms? AFAICS other IOMMU drivers could achieve the same effect fairly straightforwardly by simply copying the top-level "global" entries across whenever they switch "private" tables.

FWIW even for SMMU there could potentially be cases with Arm Ltd. IP where the SoC vendor implements a stage-2-only configuration in their media subsystem, because they care most about minimising area and stage-1-only isn't an option.


Signed-off-by: Jordan Crouse <jcro...@codeaurora.org>
  include/linux/iommu.h | 1 +
  1 file changed, 1 insertion(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 641aaf0f1b81..e2c49e583d8d 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -153,6 +153,7 @@ enum iommu_attr {
        DOMAIN_ATTR_NESTING,    /* two stages of translation */
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