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Diffstat (limited to 'Documentation/vm/hmm.rst')
| -rw-r--r-- | Documentation/vm/hmm.rst | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 09e28507f5b2..a14c2938e7af 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -332,7 +332,7 @@ between device driver specific code and shared common code: walks to fill in the ``args->src`` array with PFNs to be migrated. The ``invalidate_range_start()`` callback is passed a ``struct mmu_notifier_range`` with the ``event`` field set to - ``MMU_NOTIFY_MIGRATE`` and the ``migrate_pgmap_owner`` field set to + ``MMU_NOTIFY_MIGRATE`` and the ``owner`` field set to the ``args->pgmap_owner`` field passed to migrate_vma_setup(). This is allows the device driver to skip the invalidation callback and only invalidate device private MMU mappings that are actually migrating. @@ -405,6 +405,23 @@ between device driver specific code and shared common code: The lock can now be released. +Exclusive access memory +======================= + +Some devices have features such as atomic PTE bits that can be used to implement +atomic access to system memory. To support atomic operations to a shared virtual +memory page such a device needs access to that page which is exclusive of any +userspace access from the CPU. The ``make_device_exclusive_range()`` function +can be used to make a memory range inaccessible from userspace. + +This replaces all mappings for pages in the given range with special swap +entries. Any attempt to access the swap entry results in a fault which is +resovled by replacing the entry with the original mapping. A driver gets +notified that the mapping has been changed by MMU notifiers, after which point +it will no longer have exclusive access to the page. Exclusive access is +guranteed to last until the driver drops the page lock and page reference, at +which point any CPU faults on the page may proceed as described. + Memory cgroup (memcg) and rss accounting ======================================== |