[PATCH v2 18/24] iommu: Express DMA strictness via the domain type

Robin Murphy
2021-07-28T16:11:26Z

Eliminate the iommu_get_dma_strict() indirection and pipe the
information through the domain type from the beginning. Besides
the flow simplification this also has several nice side-effects:

- Automatically implies strict mode for untrusted devices by
virtue of their IOMMU_DOMAIN_DMA override.
- Ensures that we only end up using flush queues for drivers
which are aware of them and can actually benefit.
- Allows us to handle flush queue init failure by falling back
to strict mode instead of leaving it to possibly blow up later.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
drivers/iommu/arm/arm-smmu/arm-smmu.c | 2 +-
drivers/iommu/dma-iommu.c | 9 +++++----
drivers/iommu/iommu.c | 12 +++---------
include/linux/iommu.h | 1 -
5 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index a1f0d83d1eb5..19400826eba7 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2175,7 +2175,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
.iommu_dev = smmu->dev,
};

- if (!iommu_get_dma_strict(domain))
+ if (domain->type == IOMMU_DOMAIN_DMA_FQ)
pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;

pgtbl_ops = alloc_io_pgtable_ops(fmt, &pgtbl_cfg, smmu_domain);
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 936c5e9d5e82..109e4723f9f5 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -765,7 +765,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
.iommu_dev = smmu->dev,
};

- if (!iommu_get_dma_strict(domain))
+ if (domain->type == IOMMU_DOMAIN_DMA_FQ)
pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;

if (smmu->impl && smmu->impl->init_context) {
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 8b3545c01077..7f3968865387 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -363,13 +363,14 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,

init_iova_domain(iovad, 1UL << order, base_pfn);

- if (!cookie->fq_domain && !dev_is_untrusted(dev) &&
- domain->ops->flush_iotlb_all && !iommu_get_dma_strict(domain)) {
+ if (domain->type == IOMMU_DOMAIN_DMA_FQ && !cookie->fq_domain) {
if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all,
- iommu_dma_entry_dtor))
+ iommu_dma_entry_dtor)) {
pr_warn("iova flush queue initialization failed\n");
- else
+ domain->type = IOMMU_DOMAIN_DMA;
+ } else {
cookie->fq_domain = domain;
+ }
}

return iova_reserve_iommu_regions(dev, domain);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 982545234cf3..eecb5657de69 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -136,6 +136,9 @@ static int __init iommu_subsys_init(void)
}
}

+ if (!iommu_default_passthrough() && !iommu_dma_strict)
+ iommu_def_domain_type = IOMMU_DOMAIN_DMA_FQ;
+
pr_info("Default domain type: %s %s\n",
iommu_domain_type_str(iommu_def_domain_type),
(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
@@ -357,15 +360,6 @@ void iommu_set_dma_strict(void)
iommu_dma_strict = true;
}

-bool iommu_get_dma_strict(struct iommu_domain *domain)
-{
- /* only allow lazy flushing for DMA domains */
- if (domain->type == IOMMU_DOMAIN_DMA)
- return iommu_dma_strict;
- return true;
-}
-EXPORT_SYMBOL_GPL(iommu_get_dma_strict);
-
static ssize_t iommu_group_attr_show(struct kobject *kobj,
struct attribute *__attr, char *buf)
{
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 046ba4d54cd2..edfe2fdb8368 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -498,7 +498,6 @@ int iommu_set_pgtable_quirks(struct iommu_domain *domain,
unsigned long quirks);

void iommu_set_dma_strict(void);
-bool iommu_get_dma_strict(struct iommu_domain *domain);

extern int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
unsigned long iova, int flags);
--
2.25.1