Re: [PATCH v13 00/13] nommu UML

Tiwei Bie
2025-11-12T16:37:22Z

On Wed, 12 Nov 2025 17:52:56 +0900, Hajime Tazaki wrote:
[...]
> > However, I'm not yet convinced that all of the complexities presented in
> > this patchset (such as completely separate seccomp implementation) are
> > actually necessary in support of _just_ the second bullet. These seem to
> > me like design choices necessary to support the _first_ bullet [1].
>
> separate seccomp implementation is indeed needed due to the design
> choice we made, to use a single process to host a (um) userspace. I
> think there is no reason to unify the seccomp part because the
> signal handlers and filter installation do the different jobs.
>
> I don't see why you see this as a _complexity_, as functionally both
> seccomp handling don't interfere each other. we have prepared
> separate sub-directories for nommu to avoid unnecessary if/else
> clauses in .c/.h files.

I have the same concern about the complexities introduced by this
patch set. The new processing paths it introduces (such as the
separate handling for FP/SSE/AVX, FS, signal, syscall, ...) add a
lot of unnecessary complexities. I think Johannes's suggestion is
a great idea.

> we haven't seen any functional regressions
> since this RFC version (which was 6.12 kernel).

I took a quick look at the code. It appears that patch 02/13 will
break the mmu build when UML_TIME_TRAVEL_SUPPORT is enabled.

Regards,
Tiwei