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author | Alexandre Ghiti <alexghiti@rivosinc.com> | 2023-09-28 17:18:45 +0200 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2023-10-06 14:11:38 -0700 |
commit | 117b1bb0cbc7f5feab4fd251737869958987808c (patch) | |
tree | 9d945ace95d8bbfeedc26a7819245bf33a8b69a5 /Documentation/driver-api/media/rc-core.rst | |
parent | 824135c46b00df7fb369ec7f1f8607427bbebeb0 (diff) | |
download | linux-117b1bb0cbc7f5feab4fd251737869958987808c.tar.gz linux-117b1bb0cbc7f5feab4fd251737869958987808c.tar.bz2 linux-117b1bb0cbc7f5feab4fd251737869958987808c.zip |
riscv: handle VM_FAULT_[HWPOISON|HWPOISON_LARGE] faults instead of panicking
Patch series "Fix set_huge_pte_at()".
A recent report [1] from Ryan for arm64 revealed that we do not handle
swap entries when setting a hugepage backed by a NAPOT region (the contpte
riscv equivalent).
As explained in [1], the issue was discovered by a new test in kselftest
which uses poison entries, but the symptoms are different from arm64 though:
- the riscv kernel bugs because we do not handle VM_FAULT_HWPOISON*,
this is fixed by patch 1,
- after that, the test passes because the first pte_napot() fails (the
poison entry does not have the N bit set), and then we only set the
first page table entry covering the NAPOT hugepage, which is enough
for hugetlb_fault() to correctly raise a VM_FAULT_HWPOISON wherever we
write in this mapping since only this first page table entry is
checked
(see https://elixir.bootlin.com/linux/v6.6-rc3/source/mm/hugetlb.c#L6071).
But this seems fragile so patch 2 sets all page table entries of a
NAPOT mapping.
[1]: https://lore.kernel.org/linux-arm-kernel/20230922115804.2043771-1-ryan.roberts@arm.com/
This patch (of 2):
We used to panic when such faults were encountered but we should handle
those faults gracefully for userspace by sending a SIGBUS to the process,
like most architectures do.
Link: https://lkml.kernel.org/r/20230928151846.8229-1-alexghiti@rivosinc.com
Link: https://lkml.kernel.org/r/20230928151846.8229-2-alexghiti@rivosinc.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Andrew Jones <ajones@ventanamicro.com>
Cc: Conor Dooley <conor@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Qinglin Pan <panqinglin2020@iscas.ac.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation/driver-api/media/rc-core.rst')
0 files changed, 0 insertions, 0 deletions