Commit 68a6efe8 authored by Zhen Lei's avatar Zhen Lei Committed by Will Deacon
Browse files

iommu: Add "iommu.strict" command line option 



Add a generic command line option to enable lazy unmapping via IOVA
flush queues, which will initally be suuported by iommu-dma. This echoes
the semantics of "intel_iommu=strict" (albeit with the opposite default
value), but in the driver-agnostic fashion of "iommu.passthrough".

Signed-off-by: default avatarZhen Lei <thunder.leizhen@huawei.com>
[rm: move handling out of SMMUv3 driver, clean up documentation]
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
[will: dropped broken printk when parsing command-line option]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 2da274cd

Documentation/admin-guide/kernel-parameters.txt

+12 −0
Original line number Diff line number Diff line
@@ -1749,6 +1749,18 @@ 
		nobypass	[PPC/POWERNV]

			Disable IOMMU bypass, using IOMMU for PCI devices.



	iommu.strict=	[ARM64] Configure TLB invalidation behaviour

			Format: { "0" | "1" }

			0 - Lazy mode.

			  Request that DMA unmap operations use deferred

			  invalidation of hardware TLBs, for increased

			  throughput at the cost of reduced device isolation.

			  Will fall back to strict mode if not supported by

			  the relevant IOMMU driver.

			1 - Strict mode (default).

			  DMA unmap operations invalidate IOMMU hardware TLBs

			  synchronously.



	iommu.passthrough=

			[ARM64] Configure DMA to bypass the IOMMU by default.

			Format: { "0" | "1" }

drivers/iommu/iommu.c

+14 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY; 
#else

static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;

#endif

static bool iommu_dma_strict __read_mostly = true;



struct iommu_callback_data {

	const struct iommu_ops *ops;
@@ -131,6 +132,12 @@ static int __init iommu_set_def_domain_type(char *str) 
}

early_param("iommu.passthrough", iommu_set_def_domain_type);



static int __init iommu_dma_setup(char *str)

{

	return kstrtobool(str, &iommu_dma_strict);

}

early_param("iommu.strict", iommu_dma_setup);



static ssize_t iommu_group_attr_show(struct kobject *kobj,

				     struct attribute *__attr, char *buf)

{
@@ -1072,6 +1079,13 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev) 
		group->default_domain = dom;

		if (!group->domain)

			group->domain = dom;



		if (dom && !iommu_dma_strict) {

			int attr = 1;

			iommu_domain_set_attr(dom,

					      DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE,

					      &attr);

		}

	}



	ret = iommu_group_add_device(group, dev);

CRA Git | Maintained and supported by SUSTech CRA and CCSE