[PATCH v3 08/10] softmmu/physmem: Extend ram_block_discard_(require|disable) by two discard types

[David Hildenbrand]

We want to separate the two cases whereby we discard ram
- uncoordinated: e.g., virito-balloon
- coordinated: e.g., virtio-mem coordinated via the RamDiscardMgr

Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/exec/memory.h | 18 +++++++++++++--
 softmmu/physmem.c     | 54 ++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 64 insertions(+), 8 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 67d9f1f3a7..11832cce3c 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2808,6 +2808,12 @@ static inline MemOp devend_memop(enum device_endian end)
  */
 int ram_block_discard_disable(bool state);
 
+/*
+ * See ram_block_discard_disable(): only disable uncoordinated discards,
+ * keeping coordinated discards (via the RamDiscardMgr) enabled.
+ */
+int ram_block_uncoordinated_discard_disable(bool state);
+
 /*
  * Inhibit technologies that disable discarding of pages in RAM blocks.
  *
@@ -2817,12 +2823,20 @@ int ram_block_discard_disable(bool state);
 int ram_block_discard_require(bool state);
 
 /*
- * Test if discarding of memory in ram blocks is disabled.
+ * See ram_block_discard_require(): only inhibit technologies that disable
+ * uncoordinated discarding of pages in RAM blocks, allowing co-existance with
+ * technologies that only inhibit uncoordinated discards (via the
+ * RamDiscardMgr).
+ */
+int ram_block_coordinated_discard_require(bool state);
+
+/*
+ * Test if any 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.
+ * Test if any discarding of memory in ram blocks is required to work reliably.
  */
 bool ram_block_discard_is_required(void);
 
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 6281ef6208..3c7e6f3c53 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3660,8 +3660,14 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, 
MemoryRegion *root)
     }
 }
 
+/* Require any discards to work. */
 static unsigned int ram_block_discard_requirers;
+/* Require only coordinated discards to work. */
+static unsigned int ram_block_coordinated_discard_requirers;
+/* Disable any discards. */
 static unsigned int ram_block_discard_disablers;
+/* Disable only uncoordinated discards. */
+static unsigned int ram_block_uncoordinated_discard_disablers;
 static QemuMutex ram_block_discard_disable_mutex;
 
 static void ram_block_discard_disable_mutex_lock(void)
@@ -3687,10 +3693,27 @@ int ram_block_discard_disable(bool state)
     ram_block_discard_disable_mutex_lock();
     if (!state) {
         ram_block_discard_disablers--;
-    } else if (!ram_block_discard_requirers) {
-        ram_block_discard_disablers++;
+    } else if (ram_block_discard_requirers ||
+               ram_block_coordinated_discard_requirers) {
+        ret = -EBUSY;
     } else {
+        ram_block_discard_disablers++;
+    }
+    ram_block_discard_disable_mutex_unlock();
+    return ret;
+}
+
+int ram_block_uncoordinated_discard_disable(bool state)
+{
+    int ret = 0;
+
+    ram_block_discard_disable_mutex_lock();
+    if (!state) {
+        ram_block_uncoordinated_discard_disablers--;
+    } else if (ram_block_discard_requirers) {
         ret = -EBUSY;
+    } else {
+        ram_block_uncoordinated_discard_disablers++;
     }
     ram_block_discard_disable_mutex_unlock();
     return ret;
@@ -3703,10 +3726,27 @@ int ram_block_discard_require(bool state)
     ram_block_discard_disable_mutex_lock();
     if (!state) {
         ram_block_discard_requirers--;
-    } else if (!ram_block_discard_disablers) {
-        ram_block_discard_requirers++;
+    } else if (ram_block_discard_disablers ||
+               ram_block_uncoordinated_discard_disablers) {
+        ret = -EBUSY;
     } else {
+        ram_block_discard_requirers++;
+    }
+    ram_block_discard_disable_mutex_unlock();
+    return ret;
+}
+
+int ram_block_coordinated_discard_require(bool state)
+{
+    int ret = 0;
+
+    ram_block_discard_disable_mutex_lock();
+    if (!state) {
+        ram_block_coordinated_discard_requirers--;
+    } else if (ram_block_discard_disablers) {
         ret = -EBUSY;
+    } else {
+        ram_block_coordinated_discard_requirers++;
     }
     ram_block_discard_disable_mutex_unlock();
     return ret;
@@ -3714,10 +3754,12 @@ int ram_block_discard_require(bool state)
 
 bool ram_block_discard_is_disabled(void)
 {
-    return qatomic_read(&ram_block_discard_disablers);
+    return qatomic_read(&ram_block_discard_disablers) ||
+           qatomic_read(&ram_block_uncoordinated_discard_disablers);
 }
 
 bool ram_block_discard_is_required(void)
 {
-    return qatomic_read(&ram_block_discard_requirers);
+    return qatomic_read(&ram_block_discard_requirers) ||
+           qatomic_read(&ram_block_coordinated_discard_requirers);
 }
-- 
2.29.2