On Mon, 11 Nov 2024 at 14:27, Hajime Tazaki <thehaj...@gmail.com> wrote:
>
> This is a series of patches of nommu arch addition to UML. It would
> be nice to ask comments/opinions on this.
>
> There are still several limitations/issues which we already found;
> here is the list of those issues.
>
> - prompt configured with /etc/profile is broken (variables are not
> expanded, ${HOSTNAME%%.*}:$PWD#)
> - there are no mechanism implemented to cache for mapped memory of
> exec(2) thus, always read files from filesystem upon every exec,
> which makes slow on some benchmark (lmbench).
>
> -- Hajime
>Thanks for sending this in! I had a chance to give this a proper try with KUnit, and think it'd be a great options to have available: it's certainly nice to have a fast, easy nommu architecture for testing. I'd echo the comments from others that — at least for the testing case — it doesn't make much sense to go to the length to use the fancy zpoline patching (as neat as it is) compared to a simpler, but slower seccomp-based approach. It'd be nicer to have a simpler, more robust implementation first, and if there's a particular reason to want to speed it up later, zpoline can be added as an option. Plus, if we can avoid the need for vm.mmap_min_addr, that'd make it much easier to run the nommu tests alongside all the regular UML ones, as none would require either root, or an otherwise particularly special config. Cheers, -- David > > RFC v2: > - base branch is now uml/linux.git instead of torvalds/linux.git. > - reorganize the patch series to clean up > - fixed various coding styles issues > - clean up exec code path [07/13] > - fixed the crash/SIGSEGV case on userspace programs [10/13] > - add seccomp filter to limit syscall caller address [06/13] > - detect fsgsbase availability with sigsetjmp/siglongjmp [08/13] > - removes unrelated changes > - removes unneeded ifndef CONFIG_MMU > - convert UML_CONFIG_MMU to CONFIG_MMU as using uml/linux.git > - proposed a patch of maple-tree issue (resolving a limitation in RFC v1) > > https://lore.kernel.org/linux-mm/20241108222834.3625217-1-thehaj...@gmail.com/ > > RFC: > - https://lore.kernel.org/linux-um/cover.1729770373.git.thehaj...@gmail.com/ >
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