Hi Rob,
Appreciate your reviews/suggestions on this patch.
On 11/4/2026 9:33 PM, Rob Herring wrote:
On Tue, Nov 03, 2026 at 08:59:33PM +0530, Vikash Garodia wrote:
Reserving an IOVA address using "iommu-addresses" requires it to be
placed in the reserved-memory node. But when "iommu-addresses" is the
only property being described and there is no backing "reg" (i.e. no
actual reserved system memory), it does not really belong under
/reserved-memory. A device IOVA range is specific to its own address
space, and does not describe the system physical memory to make it
qualify under reserved-memory. Given this, place "iommu-addresses"
inside reserved-memory only when it is paired with a "reg", otherwise,
define it within the device own node. It was discussed here:
https://lore.kernel.org/all/[email protected]
Existing "iommu-addresses" property expects a phandle, which does
not make sense when the property is defined within the device node.
"iommu-ranges" was introduced to specify the device specific IOVA ranges
when there is no backing "reg".
Suggested-by: Rob Herring <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Co-developed-by: Vishnu Reddy <[email protected]>
Signed-off-by: Vishnu Reddy <[email protected]>
Signed-off-by: Vikash Garodia <[email protected]>
---
drivers/iommu/of_iommu.c | 134 +++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 125 insertions(+), 9 deletions(-)
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index
5c266511db78910d6fd221af5437cecff4931c22..0428ceb50dec58f11872b4fb64e283fa8d9046a3
100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -185,11 +185,118 @@ iommu_resv_region_get_type(struct device *dev,
if (start == phys->start && end == phys->end)
return IOMMU_RESV_DIRECT;
- dev_warn(dev, "treating non-direct mapping [%pr] -> [%pap-%pap] as reservation\n", phys,
- &start, &end);
+ dev_err(dev, "non-direct mapping [%pr] -> [%pap-%pap] is not
supported\n", phys,
+ &start, &end);
return IOMMU_RESV_RESERVED;
}
+/**
+ * of_iommu_derive_resv_regions - derive reserved regions which
+ * are outside of iommu-ranges
+ * @dev: device for which to get reserved regions
+ * @list: reserved region list
+ *
+ * A device can describe its own usable IOVA ranges directly on its node
+ * via "iommu-ranges". Everything not under those ranges is derived
+ * as a reserved region so the IOMMU allocator won't use it. Entries may
+ * appear in any order in the property.
+ */
+#if IS_ENABLED(CONFIG_OF_ADDRESS)
Is this really needed? Assuming CONFIG_OF is enabled, this is only false
on Sparc. I don't think Sparc needs anything in this file. There
aren't any IOMMU drivers for Sparc unless COMPILE_TEST is enabled. So
maybe building of_iommu.c as a whole should depend on CONFIG_OF_ADDRESS?
Agree, that's much better than adding the check, will drop from other
places too and make it conditional compilation.
Regards,
Vikash
Rob
