1 files changed, 41 insertions, 0 deletions
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 84ee5b7a01..307e527835 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2478,6 +2478,47 @@ static inline MemOp devend_memop(enum device_endian end)
 }
 #endif
 
+/*
+ * Inhibit technologies that require discarding of pages in RAM blocks, e.g.,
+ * to manage the actual amount of memory consumed by the VM (then, the memory
+ * provided by RAM blocks might be bigger than the desired memory consumption).
+ * This *must* be set if:
+ * - Discarding parts of a RAM blocks does not result in the change being
+ *   reflected in the VM and the pages getting freed.
+ * - All memory in RAM blocks is pinned or duplicated, invaldiating any previous
+ *   discards blindly.
+ * - Discarding parts of a RAM blocks will result in integrity issues (e.g.,
+ *   encrypted VMs).
+ * Technologies that only temporarily pin the current working set of a
+ * driver are fine, because we don't expect such pages to be discarded
+ * (esp. based on guest action like balloon inflation).
+ *
+ * This is *not* to be used to protect from concurrent discards (esp.,
+ * postcopy).
+ *
+ * Returns 0 if successful. Returns -EBUSY if a technology that relies on
+ * discards to work reliably is active.
+ */
+int ram_block_discard_disable(bool state);
+
+/*
+ * Inhibit technologies that disable discarding of pages in RAM blocks.
+ *
+ * Returns 0 if successful. Returns -EBUSY if discards are already set to
+ * broken.
+ */
+int ram_block_discard_require(bool state);
+
+/*
+ * Test if discarding of memory in ram blocks is disabled.
+ */
+bool ram_block_discard_is_disabled(void);
+
+/*
+ * Test if discarding of memory in ram blocks is required to work reliably.
+ */
+bool ram_block_discard_is_required(void);
+
 #endif
 
 #endif