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[PATCH v12 11/29] HMM: add discard range helper (to clear and free resources for a range).

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A common use case is for device driver to stop caring for a range of
address long before said range is munmapped by userspace program. To
avoid keeping track of such range provide an helper function that will
free HMM resources for a range of address.

NOTE THAT DEVICE DRIVER MUST MAKE SURE THE HARDWARE WILL NO LONGER
ACCESS THE RANGE BECAUSE CALLING THIS HELPER !

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
---
 include/linux/hmm.h |  3 +++
 mm/hmm.c            | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index d819ec9..10e1558 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -265,6 +265,9 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror);
 struct hmm_mirror *hmm_mirror_ref(struct hmm_mirror *mirror);
 void hmm_mirror_unref(struct hmm_mirror **mirror);
 int hmm_mirror_fault(struct hmm_mirror *mirror, struct hmm_event *event);
+void hmm_mirror_range_discard(struct hmm_mirror *mirror,
+			      unsigned long start,
+			      unsigned long end);
 
 
 #endif /* CONFIG_HMM */
diff --git a/mm/hmm.c b/mm/hmm.c
index 7b6ba6a..548f0c5 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -921,6 +921,30 @@ out:
 }
 EXPORT_SYMBOL(hmm_mirror_fault);
 
+/* hmm_mirror_range_discard() - discard a range of address.
+ *
+ * @mirror: The mirror struct.
+ * @start: Start address of the range to discard (inclusive).
+ * @end: End address of the range to discard (exclusive).
+ *
+ * Call when device driver want to stop mirroring a range of address and free
+ * any HMM resources associated with that range (including dma mapping if any).
+ *
+ * THIS FUNCTION ASSUME THAT DRIVER ALREADY STOPPED USING THE RANGE OF ADDRESS
+ * AND THUS DO NOT PERFORM ANY SYNCHRONIZATION OR UPDATE WITH THE DRIVER TO
+ * INVALIDATE SAID RANGE.
+ */
+void hmm_mirror_range_discard(struct hmm_mirror *mirror,
+			      unsigned long start,
+			      unsigned long end)
+{
+	struct hmm_event event;
+
+	hmm_event_init(&event, mirror->hmm, start, end, HMM_MUNMAP);
+	hmm_mirror_update_pt(mirror, &event, NULL);
+}
+EXPORT_SYMBOL(hmm_mirror_range_discard);
+
 /* hmm_mirror_register() - register mirror against current process for a device.
  *
  * @mirror: The mirror struct being registered.
-- 
2.4.3

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HMM (Heterogeneous Memory Management) Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 11/29] HMM: add discard range helper (to clear and free resources for a range). Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 19/29] HMM: add new HMM page table flag (select flag). Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 03/29] mmu_notifier: pass page pointer to mmu_notifier_invalidate_page() v2 Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 05/29] HMM: introduce heterogeneous memory management v5. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 06/29] HMM: add HMM page table v4. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 10/29] HMM: use CPU page table during invalidation. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 29/29] HMM: add mirror fault support for system to device memory migration v3. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 24/29] HMM: allow to get pointer to spinlock protecting a directory. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 07/29] HMM: add per mirror page table v4. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 15/29] HMM: add documentation explaining HMM internals and how to use it. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 17/29] HMM: add special swap filetype for memory migrated to device v2. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 21/29] HMM: mm add helper to update page table when migrating memory back v2. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100
  [PATCH v12 23/29] HMM: new callback for copying memory from and to device memory v2. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 13/29] HMM: DMA map memory on behalf of device driver v2. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 14/29] HMM: Add support for hugetlb. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 28/29] HMM: CPU page fault on migrated memory. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 26/29] HMM: add helpers for migration back to system memory v3. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 25/29] HMM: split DMA mapping function in two. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 08/29] HMM: add device page fault support v6. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 18/29] HMM: add new HMM page table flag (valid device memory). Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 12/29] HMM: add dirty range helper (toggle dirty bit inside mirror page table) v2. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100
  [PATCH v12 20/29] HMM: handle HMM device page table entry on mirror page table fault and update. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 21:00 +0100

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