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authorAlexandre Ghiti <alexghiti@rivosinc.com>2023-09-28 18:18:45 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-10-07 00:11:38 +0300
commit117b1bb0cbc7f5feab4fd251737869958987808c (patch)
tree9d945ace95d8bbfeedc26a7819245bf33a8b69a5 /arch/riscv
parent824135c46b00df7fb369ec7f1f8607427bbebeb0 (diff)
downloadlinux-117b1bb0cbc7f5feab4fd251737869958987808c.tar.xz
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 'arch/riscv')
-rw-r--r--arch/riscv/mm/fault.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 6115d7514972..90d4ba36d1d0 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -72,7 +72,7 @@ static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_f
}
pagefault_out_of_memory();
return;
- } else if (fault & VM_FAULT_SIGBUS) {
+ } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs)) {
no_context(regs, addr);