Messages in this thread Patch in this message | | | From | Nadav Amit <> | Subject | [RFC PATCH 02/14] userfaultfd: try to map write-unprotected pages | Date | Mon, 18 Jul 2022 05:02:00 -0700 |
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From: Nadav Amit <namit@vmware.com>
When using userfaultfd write-(un)protect ioctl, try to change the PTE to be writable. This would save a page-fault afterwards.
Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Cc: Yu Zhao <yuzhao@google.com> Cc: Nick Piggin <npiggin@gmail.com> Signed-off-by: Nadav Amit <namit@vmware.com> --- mm/userfaultfd.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e0492f5f06a0..6013b217e9f3 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -799,6 +799,8 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, cp_flags = enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE; if (uffd_flags & (UFFD_FLAGS_ACCESS_LIKELY|UFFD_FLAGS_WRITE_LIKELY)) cp_flags |= MM_CP_WILL_NEED; + if (!enable_wp && (uffd_flags & UFFD_FLAGS_WRITE_LIKELY)) + cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; tlb_gather_mmu(&tlb, dst_mm); change_protection(&tlb, dst_vma, start, start + len, newprot, cp_flags); -- 2.25.1
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