From: Robin Murphy <robin.murphy@arm.com>
Date: Wed, 11 Aug 2021 13:21:35 +0100
Subject: iommu: Expose DMA domain strictness via sysfs
Git-commit: 26225bea1d84b090b378838a1797daec62d4ad0e
Patch-mainline: v5.15-rc1
References: bsc#1192202
The sysfs interface for default domain types exists primarily so users
can choose the performance/security tradeoff relevant to their own
workload. As such, the choice between the policies for DMA domains fits
perfectly as an additional point on that scale - downgrading a
particular device from a strict default to non-strict may be enough to
let it reach the desired level of performance, while still retaining
more peace of mind than with a wide-open identity domain. Now that we've
abstracted non-strict mode as a distinct type of DMA domain, allow it to
be chosen through the user interface as well.
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/0e08da5ed4069fd3473cfbadda758ca983becdbf.1628682049.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
Documentation/ABI/testing/sysfs-kernel-iommu_groups | 6 +++++-
drivers/iommu/iommu.c | 2 ++
2 files changed, 7 insertions(+), 1 deletion(-)
--- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups
+++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
@@ -42,8 +42,12 @@ Description: /sys/kernel/iommu_groups/<g
======== ======================================================
DMA All the DMA transactions from the device in this group
are translated by the iommu.
+ DMA-FQ As above, but using batched invalidation to lazily
+ remove translations after use. This may offer reduced
+ overhead at the cost of reduced memory protection.
identity All the DMA transactions from the device in this group
- are not translated by the iommu.
+ are not translated by the iommu. Maximum performance
+ but zero protection.
auto Change to the type the device was booted with.
======== ======================================================
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3273,6 +3273,8 @@ static ssize_t iommu_group_store_type(st
req_type = IOMMU_DOMAIN_IDENTITY;
else if (sysfs_streq(buf, "DMA"))
req_type = IOMMU_DOMAIN_DMA;
+ else if (sysfs_streq(buf, "DMA-FQ"))
+ req_type = IOMMU_DOMAIN_DMA_FQ;
else if (sysfs_streq(buf, "auto"))
req_type = 0;
else