Hi Niklas,

On Mon, Oct 13, 2025 at 11:53:55AM +0200, Niklas Schnelle wrote:

On Sun, 2025-10-12 at 17:04 -0700, Nicolin Chen wrote:

quoted

Add a new test_dev domain op for driver to test the compatibility between
a domain and a device at the driver level, before calling into the actual
attachment/replacement of a domain. Support pasid for set_dev_pasid call.

Move existing core-level compatibility tests to a helper function. Invoke
it prior to:
 * __iommu_attach_device() or its wrapper __iommu_device_set_domain()
 * __iommu_set_group_pasid()

Should this list also include iommu_deferred_attach()? The code does
include it.

iommu_deferred_attach() invokes __iommu_attach_device(), so it is
already included in the list :)

quoted

 /**
  * struct iommu_domain_ops - domain specific operations
- * @attach_dev: attach an iommu domain to a device
+ * @test_dev: Test compatibility prior to an @attach_dev or @set_dev_pasid call.
+ *            A driver-level callback of this op should do a thorough sanity, to

You're missing the word "check" above.

Ack.

quoted

+ *            make sure a device is compatible with the domain. So the following
+ *            @attach_dev and @set_dev_pasid functions would likely succeed with
+ *            only one exception due to a temporary failure like out of memory.

Nit: "… only one exception …" / "… like out of memory …" this sounds a
bit odd to me because on the one hand it's one exception but then also
a group (temporary failures).

Maybe better:
"… would likely succeed with only the exception of temporary failures
like out of memory."?

Sure. I can do that. Fixing both parts, it would be:

 * @test_dev: Test compatibility prior to an @attach_dev or @set_dev_pasid call.
 *            A driver callback of this op should do a thorough sanity check, to
 *            make sure a device is compatible with the domain, so the following
 *            @attach_dev and @set_dev_pasid functions would likely succeed with
 *            only the exception of temporary failures like out of memory.

Thanks for the review!
Nicolin