diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2017-01-27 12:22:54 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2017-04-06 16:06:42 +0100 |
| commit | adf5e5168bd51c42332ebaa709351fa6ed65ea73 (patch) | |
| tree | 135872dcba7da5019c11c857cb11ca8321fbdc82 /include/linux/iommu.h | |
| parent | c02ed2e75ef4c74e41e421acb4ef1494671585e8 (diff) | |
iommu: Better document the IOMMU_PRIV flag
This is a fairly subtle thing - let's make sure it's described as
clearly as possible to avoid potential misunderstandings.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'include/linux/iommu.h')
| -rw-r--r-- | include/linux/iommu.h | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 2e4de0deee53..88ec8c6580d3 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -32,10 +32,13 @@ #define IOMMU_NOEXEC (1 << 3) #define IOMMU_MMIO (1 << 4) /* e.g. things like MSI doorbells */ /* - * This is to make the IOMMU API setup privileged - * mapppings accessible by the master only at higher - * privileged execution level and inaccessible at - * less privileged levels. + * Where the bus hardware includes a privilege level as part of its access type + * markings, and certain devices are capable of issuing transactions marked as + * either 'supervisor' or 'user', the IOMMU_PRIV flag requests that the other + * given permission flags only apply to accesses at the higher privilege level, + * and that unprivileged transactions should have as little access as possible. + * This would usually imply the same permissions as kernel mappings on the CPU, + * if the IOMMU page table format is equivalent. */ #define IOMMU_PRIV (1 << 5) |