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Subject[PATCH 11/36] HMM: add discard range helper (to clear and free resources for a range).
Date
From: Jérôme Glisse <jglisse@redhat.com>

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 fdb1975..ec05df8 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -250,6 +250,9 @@ struct hmm_mirror {
int hmm_mirror_register(struct hmm_mirror *mirror);
void hmm_mirror_unregister(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 8ec9ffa..4cab3f2 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -916,6 +916,30 @@ 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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