[PATCH v1 05/17] virtio-balloon: Rip out qemu_balloon_inhibit()

[David Hildenbrand <david@xxxxxxxxxx>]

The only remaining special case is postcopy. It cannot handle
concurrent discards yet, which would result in requesting already sent
pages from the source. Special-case it in virtio-balloon instead.

Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Juan Quintela <quintela@xxxxxxxxxx>
Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 balloon.c                  | 18 ------------------
 hw/virtio/virtio-balloon.c | 12 +++++++++++-
 include/sysemu/balloon.h   |  2 --
 migration/postcopy-ram.c   | 23 -----------------------
 4 files changed, 11 insertions(+), 44 deletions(-)

diff --git a/balloon.c b/balloon.c
index c49f57c27b..354408c6ea 100644
--- a/balloon.c
+++ b/balloon.c
@@ -36,24 +36,6 @@
 static QEMUBalloonEvent *balloon_event_fn;
 static QEMUBalloonStatus *balloon_stat_fn;
 static void *balloon_opaque;
-static int balloon_inhibit_count;
-
-bool qemu_balloon_is_inhibited(void)
-{
-    return atomic_read(&balloon_inhibit_count) > 0 ||
-           ram_block_discard_is_broken();
-}
-
-void qemu_balloon_inhibit(bool state)
-{
-    if (state) {
-        atomic_inc(&balloon_inhibit_count);
-    } else {
-        atomic_dec(&balloon_inhibit_count);
-    }
-
-    assert(atomic_read(&balloon_inhibit_count) >= 0);
-}
 
 static bool have_balloon(Error **errp)
 {
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a4729f7fc9..aa5b89fb47 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -29,6 +29,7 @@
 #include "trace.h"
 #include "qemu/error-report.h"
 #include "migration/misc.h"
+#include "migration/postcopy-ram.h"
 
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
@@ -63,6 +64,15 @@ static bool virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
     return pbp->base_gpa == base_gpa;
 }
 
+static bool virtio_balloon_inhibited(void)
+{
+    PostcopyState ps = postcopy_state_get();
+
+    /* Postcopy cannot deal with concurrent discards (yet), so it's special. */
+    return ram_block_discard_is_broken() ||
+           (ps >= POSTCOPY_INCOMING_DISCARD && ps < POSTCOPY_INCOMING_END);
+}
+
 static void balloon_inflate_page(VirtIOBalloon *balloon,
                                  MemoryRegion *mr, hwaddr mr_offset,
                                  PartiallyBalloonedPage *pbp)
@@ -360,7 +370,7 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 
             trace_virtio_balloon_handle_output(memory_region_name(section.mr),
                                                pa);
-            if (!qemu_balloon_is_inhibited()) {
+            if (!virtio_balloon_inhibited()) {
                 if (vq == s->ivq) {
                     balloon_inflate_page(s, section.mr,
                                          section.offset_within_region, &pbp);
diff --git a/include/sysemu/balloon.h b/include/sysemu/balloon.h
index aea0c44985..20a2defe3a 100644
--- a/include/sysemu/balloon.h
+++ b/include/sysemu/balloon.h
@@ -23,7 +23,5 @@ typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
                              QEMUBalloonStatus *stat_func, void *opaque);
 void qemu_remove_balloon_handler(void *opaque);
-bool qemu_balloon_is_inhibited(void);
-void qemu_balloon_inhibit(bool state);
 
 #endif
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a36402722b..b41a9fe2fd 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -27,7 +27,6 @@
 #include "qemu/notify.h"
 #include "qemu/rcu.h"
 #include "sysemu/sysemu.h"
-#include "sysemu/balloon.h"
 #include "qemu/error-report.h"
 #include "trace.h"
 #include "hw/boards.h"
@@ -520,20 +519,6 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis)
     return 0;
 }
 
-/*
- * Manage a single vote to the QEMU balloon inhibitor for all postcopy usage,
- * last caller wins.
- */
-static void postcopy_balloon_inhibit(bool state)
-{
-    static bool cur_state = false;
-
-    if (state != cur_state) {
-        qemu_balloon_inhibit(state);
-        cur_state = state;
-    }
-}
-
 /*
  * At the end of a migration where postcopy_ram_incoming_init was called.
  */
@@ -565,8 +550,6 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
         mis->have_fault_thread = false;
     }
 
-    postcopy_balloon_inhibit(false);
-
     if (enable_mlock) {
         if (os_mlock() < 0) {
             error_report("mlock: %s", strerror(errno));
@@ -1160,12 +1143,6 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
     }
     memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
 
-    /*
-     * Ballooning can mark pages as absent while we're postcopying
-     * that would cause false userfaults.
-     */
-    postcopy_balloon_inhibit(true);
-
     trace_postcopy_ram_enable_notify();
 
     return 0;
-- 
2.25.3