On 01/09/2025 9:56 am, Jan Beulich wrote:
> With the processing done linearly (rather than recursively), checking
> whether any of the features was previously seen is wrong: That would
> e.g. trigger for this simple set of dependencies
>
> X: [A, B]
> A: [C]
> B: [C]
>
> (observed in reality when making AMX-AVX512 dependent upon both
> AMX-TILE and AVX512F, causing XSAVE to see AMX-AVX512 twice in its list
> of dependents). But checking the whole accumulated set also isn't
> necessary - just checking the feature we're processing dependents of is
> sufficient. We may detect a cycle later that way, but we still will
> detect it. What we need to avoid is adding a feature again when we've
> already seen it.
>
> As a result, seeding "seen[]" with "feat" isn't necessary anymore.
>
> Fixes: fe4408d180f4 ("xen/x86: Generate deep dependencies of features")
> Signed-off-by: Jan Beulich <[email protected]>
Acked-by: Andrew Cooper <[email protected]>, with one further
minor adjustment.
> --- a/xen/tools/gen-cpuid.py
> +++ b/xen/tools/gen-cpuid.py
> @@ -379,14 +379,17 @@ def crunch_numbers(state):
>
> f = to_process.pop(0)
>
> + if f == feat:
> + raise Fail("ERROR: Cycle found when processing %s" % \
No need for the \ here.
~Andrew
