Changeset 16464 in vbox

Timestamp:

Feb 2, 2009 2:53:14 PM (16 years ago)

Author:

vboxsync

Message:

set VM_LOCKED to pin pages allocated with mmap()

File:

• trunk/src/VBox/Runtime/r0drv/linux/memobj-r0drv-linux.c (modified) (2 diffs)

trunk/src/VBox/Runtime/r0drv/linux/memobj-r0drv-linux.c

@@ -744 +744 @@
         {
             /*
-             * Flush dcache (required?) and protect against fork.
+             * Flush dcache (required?), protect against fork and _really_ pin the page
+             * table entries. get_user_pages() will protect against swapping out the
+             * pages but it will NOT protect against removing page table entries. This
+             * can be achieved with
+             *   - using mlock / mmap(..., MAP_LOCKED, ...) from userland. This requires
+             *     an appropriate limit set up with setrlimit(..., RLIMIT_MEMLOCK, ...).
+             *     Usual Linux distributions support only a limited size of locked pages
+             *     (e.g. 32KB).
+             *   - setting the PageReserved bit (as we do in rtR0MemObjLinuxAllocPages()
+             *     or by
+             *   - setting the VM_LOCKED flag. This is the same as doing mlock() without
+             *     a range check.
              */
             /** @todo The Linux fork() protection will require more work if this API
@@ -751 +762 @@
             {
                 flush_dcache_page(pMemLnx->apPages[rc]);
-                papVMAs[rc]->vm_flags |= VM_DONTCOPY;
+                papVMAs[rc]->vm_flags |= (VM_DONTCOPY | VM_LOCKED);
             }