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90a7592da1
s390x must disable shared zeropages for processes running VMs, because the VMs could end up making use of "storage keys" or protected virtualization, which are incompatible with shared zeropages. Yet, with userfaultfd it is possible to insert shared zeropages into such processes. Let's fallback to simply allocating a fresh zeroed anonymous folio and insert that instead. mm_forbids_zeropage() was introduced in commit593befa6ab("mm: introduce mm_forbids_zeropage function"), briefly before userfaultfd went upstream. Note that we don't want to fail the UFFDIO_ZEROPAGE request like we do for hugetlb, it would be rather unexpected. Further, we also cannot really indicated "not supported" to user space ahead of time: it could be that the MM disallows zeropages after userfaultfd was already registered. [ agordeev: Fixed checkpatch complaints ] Fixes:c1a4de99fa("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") Reviewed-by: Peter Xu <peterx@redhat.com> Link: https://lore.kernel.org/r/20240411161441.910170-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.