kernel/tools/testing/selftests/vm/cow.c, branch linux-6.2.y

selftests/vm: cow: fix compile warning on 32bit

2022-12-12T02:12:20Z

The compiler complains about the conversion of a pointer to an int of different width. Link: https://lkml.kernel.org/r/20221205193716.276024-4-david@redhat.com Fixes: 6f1405efc61b ("selftests/vm: anon_cow: add R/O longterm tests via gup_test") Signed-off-by: David Hildenbrand Cc: Shuah Khan Cc: Yang Li Signed-off-by: Andrew Morton

selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages

2022-11-30T23:58:57Z

Let's test whether R/O long-term pinning is reliable for non-anonymous memory: when R/O long-term pinning a page, the expectation is that we break COW early before pinning, such that actual write access via the page tables won't break COW later and end up replacing the R/O-pinned page in the page table. Consequently, R/O long-term pinning in private mappings would only target exclusive anonymous pages. For now, all tests fail: # [RUN] R/O longterm GUP pin ... with shared zeropage not ok 151 Longterm R/O pin is reliable # [RUN] R/O longterm GUP pin ... with memfd not ok 152 Longterm R/O pin is reliable # [RUN] R/O longterm GUP pin ... with tmpfile not ok 153 Longterm R/O pin is reliable # [RUN] R/O longterm GUP pin ... with huge zeropage not ok 154 Longterm R/O pin is reliable # [RUN] R/O longterm GUP pin ... with memfd hugetlb (2048 kB) not ok 155 Longterm R/O pin is reliable # [RUN] R/O longterm GUP pin ... with memfd hugetlb (1048576 kB) not ok 156 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with shared zeropage not ok 157 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with memfd not ok 158 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with tmpfile not ok 159 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with huge zeropage not ok 160 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (2048 kB) not ok 161 Longterm R/O pin is reliable # [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (1048576 kB) not ok 162 Longterm R/O pin is reliable Link: https://lkml.kernel.org/r/20221116102659.70287-4-david@redhat.com Signed-off-by: David Hildenbrand Signed-off-by: Andrew Morton

selftests/vm: cow: basic COW tests for non-anonymous pages

2022-11-30T23:58:57Z

Let's add basic tests for COW with non-anonymous pages in private mappings: write access should properly trigger COW and result in the private changes not being visible through other page mappings. Especially, add tests for: * Zeropage * Huge zeropage * Ordinary pagecache pages via memfd and tmpfile() * Hugetlb pages via memfd Fortunately, all tests pass. Link: https://lkml.kernel.org/r/20221116102659.70287-3-david@redhat.com Signed-off-by: David Hildenbrand Signed-off-by: Andrew Morton

selftests/vm: anon_cow: prepare for non-anonymous COW tests

2022-11-30T23:58:56Z

Patch series "mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning)". For now, we did not support reliable R/O long-term pinning in COW mappings. That means, if we would trigger R/O long-term pinning in MAP_PRIVATE mapping, we could end up pinning the (R/O-mapped) shared zeropage or a pagecache page. The next write access would trigger a write fault and replace the pinned page by an exclusive anonymous page in the process page table; whatever the process would write to that private page copy would not be visible by the owner of the previous page pin: for example, RDMA could read stale data. The end result is essentially an unexpected and hard-to-debug memory corruption. Some drivers tried working around that limitation by using "FOLL_FORCE|FOLL_WRITE|FOLL_LONGTERM" for R/O long-term pinning for now. FOLL_WRITE would trigger a write fault, if required, and break COW before pinning the page. FOLL_FORCE is required because the VMA might lack write permissions, and drivers wanted to make that working as well, just like one would expect (no write access, but still triggering a write access to break COW). However, that is not a practical solution, because (1) Drivers that don't stick to that undocumented and debatable pattern would still run into that issue. For example, VFIO only uses FOLL_LONGTERM for R/O long-term pinning. (2) Using FOLL_WRITE just to work around a COW mapping + page pinning limitation is unintuitive. FOLL_WRITE would, for example, mark the page softdirty or trigger uffd-wp, even though, there actually isn't going to be any write access. (3) The purpose of FOLL_FORCE is debug access, not access without lack of VMA permissions by arbitrarty drivers. So instead, make R/O long-term pinning work as expected, by breaking COW in a COW mapping early, such that we can remove any FOLL_FORCE usage from drivers and make FOLL_FORCE ptrace-specific (renaming it to FOLL_PTRACE). More details in patch #8. This patch (of 19): Originally, the plan was to have a separate tests for testing COW of non-anonymous (e.g., shared zeropage) pages. Turns out, that we'd need a lot of similar functionality and that there isn't a really good reason to separate it. So let's prepare for non-anon tests by renaming to "cow". Link: https://lkml.kernel.org/r/20221116102659.70287-1-david@redhat.com Link: https://lkml.kernel.org/r/20221116102659.70287-2-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Vlastimil Babka Cc: Alexander Shishkin Cc: Alexander Viro Cc: Alex Williamson Cc: Andrea Arcangeli Cc: Andy Walls Cc: Anton Ivanov Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Bernard Metzler Cc: Borislav Petkov Cc: Catalin Marinas Cc: Christian Benvenuti Cc: Christian Gmeiner Cc: Christophe Leroy Cc: Christoph Hellwig Cc: Daniel Vetter Cc: Daniel Vetter Cc: Dave Hansen Cc: David Airlie Cc: David S. Miller Cc: Dennis Dalessandro Cc: "Eric W . Biederman" Cc: Greg Kroah-Hartman Cc: Hans Verkuil Cc: "H. Peter Anvin" Cc: Hugh Dickins Cc: Ingo Molnar Cc: Inki Dae Cc: Ivan Kokshaysky Cc: James Morris Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: Johannes Berg Cc: John Hubbard Cc: Kees Cook Cc: Kentaro Takeda Cc: Krzysztof Kozlowski Cc: Kyungmin Park Cc: Leon Romanovsky Cc: Leon Romanovsky Cc: Linus Torvalds Cc: Lucas Stach Cc: Marek Szyprowski Cc: Mark Rutland Cc: Matthew Wilcox Cc: Matt Turner Cc: Mauro Carvalho Chehab Cc: Michael Ellerman Cc: Mike Kravetz Cc: Muchun Song Cc: Nadav Amit Cc: Namhyung Kim Cc: Nelson Escobar Cc: Nicholas Piggin Cc: Oded Gabbay Cc: Oleg Nesterov Cc: Paul Moore Cc: Peter Xu Cc: Peter Zijlstra Cc: Richard Henderson Cc: Richard Weinberger Cc: Russell King Cc: Serge Hallyn Cc: Seung-Woo Kim Cc: Shuah Khan Cc: Tetsuo Handa Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Tomasz Figa Cc: Will Deacon Signed-off-by: Andrew Morton