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[PATCH 11/15] 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 d652233..f271441 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -896,6 +896,30 @@ 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.
-- 
1.9.3

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Thread

HMM (Heterogeneous Memory Management) v10 Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 13/15] HMM: DMA map memory on behalf of device driver v2. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 03/15] mmu_notifier: pass page pointer to mmu_notifier_invalidate_page() v2 Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 08/15] HMM: add device page fault support v4. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 09/15] HMM: add mm page table iterator helpers. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 15/15] hmm/dummy: dummy driver for testing and showcasing the HMM API Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 14/15] HMM: add documentation explaining HMM internals and how to use it. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 10/15] HMM: use CPU page table during invalidation. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 11/15] HMM: add discard range helper (to clear and free resources for a range). Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 06/15] HMM: add HMM page table v4. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 07/15] HMM: add per mirror page table v4. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200
  [PATCH 12/15] HMM: add dirty range helper (toggle dirty bit inside mirror page table) v2. Jérôme Glisse <jglisse@redhat.com> - 2015-08-13 21:20 +0200

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