Hi Robin, >-----Original Message----- >From: linux-arm-kernel [mailto:[email protected]] >On Behalf Of Robin Murphy >Sent: Friday, January 27, 2017 5:53 PM >To: [email protected] >Cc: [email protected]; [email protected]; >[email protected] >Subject: [PATCH] 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 <[email protected]> >--- > >Having another look through the IOMMU_PRIV series, I wasn't convinced >that the original comment was really all that helpful - I'm happy for >this to be squashed in if you like. > >Robin. > > include/linux/iommu.h | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > >diff --git a/include/linux/iommu.h b/include/linux/iommu.h >index 69e2417a2965..3c830e153069 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. > */
Agree, gives much more insight. Regards, Sricharan _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
