Re: [PATCH v2 0/3] kho: Add support for kunit mocking KHO restore API

[Mike Rapoport <rppt@kernel.org>]

Hi Samiullah,

On Thu, May 21, 2026 at 07:31:59PM +0000, Samiullah Khawaja wrote:
> To write kunit tests for preservation and restoration of liveupdate
> state in various subsystems without triggering the actual kexec, the KHO
> restore API needs to be mocked by the test writer. The mocking is done
> to allow testing of the individual components or functions in isolation.
> 
> The patch series adds the following to support kunit testing when using the KHO
> API:
> 
> - Add static stub hooks to mock the KHO restore API so the restore path
>   can be tested without triggering kexec.
> - Add helper function that can be used by the test writer to check if
>   memory is preserved in KHO tree.
> 
> Finally, it adds a KUnit test for the KHO API that verifies the allocation of
> preserved memory, and the preservation/restoration of pages and folios.

I looked at the tests for preservation and apparently they don't add
coverage beyond the existing KHO selftest. How hard and/or intrusive would
be adding tests for example for error paths?

Do you have an example of a kunit test for another subsystem that would
benefit from mocking of KHO APIs?
 
> KHO Kunit test run:
> 
>  KTAP version 1
>  1..1
>      KTAP version 1
>      # Subtest: kho_test
>      # module: kexec_handover_test
>      1..3
>      ok 1 kho_test_alloc_preserve
>      ok 2 kho_test_preserve_pages
>      ok 3 kho_test_preserve_folio
>  # kho_test: pass:3 fail:0 skip:0 total:3
>  # Totals: pass:3 fail:0 skip:0 total:3
>  ok 1 kho_test
> 
> v2:
>  - Move kunit header includes above linux header includes.
>  - Use the __kho_preserve_pages_order() to get the order of preserved
>    pages instead of open order calculation math.
> 
> Samiullah Khawaja (3):
>   kho: Add kunit static stubs
>   kho: Add helper function to check if pages are preserved
>   kho: Add kunit test to verify preserve/restore pages and folio
> 
>  include/linux/kexec_handover.h          |   5 +
>  kernel/liveupdate/Kconfig               |  10 ++
>  kernel/liveupdate/Makefile              |   1 +
>  kernel/liveupdate/kexec_handover.c      |  63 +++++++++++-
>  kernel/liveupdate/kexec_handover_test.c | 131 ++++++++++++++++++++++++
>  5 files changed, 209 insertions(+), 1 deletion(-)
>  create mode 100644 kernel/liveupdate/kexec_handover_test.c
> 
> 
> base-commit: ec4084bc445027a52f600e30a976928be1ba1950
> -- 
> 2.54.0.746.g67dd491aae-goog
> 

-- 
Sincerely yours,
Mike.