diff mbox series

[RFC,02/14] userfaultfd: try to map write-unprotected pages

Message ID 20220718120212.3180-3-namit@vmware.com (mailing list archive)
State New
Headers show
Series [RFC,01/14] userfaultfd: set dirty and young on writeprotect | expand

Commit Message

Nadav Amit July 18, 2022, 12:02 p.m. UTC 
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(+)

Comments

Peter Xu July 19, 2022, 8:49 p.m. UTC | #1 
On Mon, Jul 18, 2022 at 05:02:00AM -0700, Nadav Amit wrote:
> 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>

Acked-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

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);