On Mon, Nov 07, 2022 at 08:49:08PM -0400, Jason Gunthorpe wrote:

Cover the essential functionality of the iommufd with a directed test. This aims to achieve reasonable functional coverage using the in-kernel self test framework.

It provides a mock kernel module for the iommu_domain that allows it to run without any HW and the mocking provides a way to directly validate that the PFNs loaded into the iommu_domain are correct.

The mock also simulates the rare case of PAGE_SIZE > iommu page size as the mock will operate at a 2K iommu page size. This allows exercising all of the calculations to support this mismatch.

This allows achieving high coverage of the corner cases in the iopt_pages.

However, it is an unusually invasive config option to enable all of this. The config option should not be enabled in a production kernel.

This patch crossed 100k so it was bounced from the vger lists.

If anyone didn't get it and would like to see it lore has it:

https://lore.kernel.org/linux-iommu/15-v4-0de2f6c78ed0+9d1-iommufd_jgg@nvidi...

For the eventual v5 I will split the nth test into its own patch

Jason