Commit 26225bea authored by Robin Murphy's avatar Robin Murphy Committed by Joerg Roedel
Browse files

iommu: Expose DMA domain strictness via sysfs 



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: default avatarLu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: default avatarJohn Garry <john.garry@huawei.com>
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/0e08da5ed4069fd3473cfbadda758ca983becdbf.1628682049.git.robin.murphy@arm.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent c208916f

Documentation/ABI/testing/sysfs-kernel-iommu_groups

+5 −1
Original line number Diff line number Diff line
@@ -42,8 +42,12 @@ Description: /sys/kernel/iommu_groups/<grp_id>/type shows the type of default 
		========  ======================================================

		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.

		========  ======================================================

drivers/iommu/iommu.c

+2 −0
Original line number Diff line number Diff line
@@ -3268,6 +3268,8 @@ static ssize_t iommu_group_store_type(struct iommu_group *group, 
		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