On 16/10/2026 7:46 am, Mikko Perttunen wrote:
ARM's arch_setup_dma_ops / arm_setup_iommu_dma_ops creates a custom
IOMMU domain for DMA API usage, and continues to do so when the IOMMU
driver doesn't explicitly request a DMA default domain type.
When, however, that DMA default domain is requested and the core owns
the domain, we need to skip our own domain management. Add checks to
arm_setup/teardown_iommu_dma_ops for these cases. In such a case IOVAs
can be allocated from anywhere in the domain's geometry, so also add a
check to ensure the device's dma-ranges cover it. Presently, this is the
case for all platforms except some OMAP platforms with a non-zero
dma-ranges base.
It's probably worth adding some cleverness to arm_iommu_detach_device()
as well - it might work out benign to attempt to detach from a real
core-owned default domain, but we'll now want to set dma_ops and
to_dma_iommu_mapping according to the default domain itself (since we'll
now have the possibility of switching between an explicit unmanaged
dma_iommu_mapping and the implicit default one.)
Thanks,
Robin.
Signed-off-by: Mikko Perttunen <[email protected]>
---
arch/arm/mm/dma-mapping.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f2d3e8ec3487..d6315baeddb9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1761,13 +1761,33 @@ EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
static void arm_setup_iommu_dma_ops(struct device *dev)
{
- struct dma_iommu_mapping *mapping;
+ struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
u64 dma_base = 0, size = 1ULL << 32;
if (dev->dma_range_map) {
dma_base = dma_range_map_min(dev->dma_range_map);
size = dma_range_map_max(dev->dma_range_map) - dma_base;
}
+
+ /*
+ * An existing cookie means the core owns the domain. Only set the
+ * per-binding DMA ops. IOVAs are allocated from the whole aperture,
+ * so the device's dma-ranges must cover it.
+ */
+ if (mapping) {
+ const struct iommu_domain_geometry *geo =
+ &mapping->domain->geometry;
+
+ if (dma_base > geo->aperture_start ||
+ dma_base + size < geo->aperture_end) {
+ dev_err(dev, "dma-ranges do not cover the IOMMU
aperture\n");
+ return;
+ }
+
+ set_dma_ops(dev, &iommu_ops);
+ return;
+ }
+
mapping = arm_iommu_create_mapping(dev, dma_base, size);
if (IS_ERR(mapping)) {
pr_warn("Failed to create %llu-byte IOMMU mapping for device
%s\n",
@@ -1792,6 +1812,9 @@ static void arm_teardown_iommu_dma_ops(struct device *dev)
if (!mapping)
return;
+ if (!mapping->owns_domain)
+ return;
+
arm_iommu_detach_device(dev);
arm_iommu_release_mapping(mapping);
}
