[PATCH v3 05/20] virtio-balloon: Rip out qemu_balloon_inhibit()

David Hildenbrand
2020-06-03T14:50:07Z

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.

Introduce migration_in_incoming_postcopy(), to find out if incoming
postcopy is active.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
balloon.c | 18 ------------------
hw/virtio/virtio-balloon.c | 8 +++++++-
include/migration/misc.h | 2 ++
include/sysemu/balloon.h | 2 --
migration/migration.c | 7 +++++++
migration/postcopy-ram.c | 23 -----------------------
6 files changed, 16 insertions(+), 44 deletions(-)

diff --git a/balloon.c b/balloon.c
index 5fff79523a..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_disabled();
-}
-
-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 065cd450f1..5ce2f956df 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -63,6 +63,12 @@ static bool virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
return pbp->base_gpa == base_gpa;
}

+static bool virtio_balloon_inhibited(void)
+{
+ /* Postcopy cannot deal with concurrent discards, so it's special. */
+ return ram_block_discard_is_disabled() || migration_in_incoming_postcopy();
+}
+
static void balloon_inflate_page(VirtIOBalloon *balloon,
MemoryRegion *mr, hwaddr mr_offset,
PartiallyBalloonedPage *pbp)
@@ -360,7 +366,7 @@ 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/migration/misc.h b/include/migration/misc.h
index d2762257aa..34e7d75713 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -69,6 +69,8 @@ bool migration_has_failed(MigrationState *);
/* ...and after the device transmission */
bool migration_in_postcopy_after_devices(MigrationState *);
void migration_global_dump(Monitor *mon);
+/* True if incomming migration entered POSTCOPY_INCOMING_DISCARD */
+bool migration_in_incoming_postcopy(void);

/* migration/block-dirty-bitmap.c */
void dirty_bitmap_mig_init(void);
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/migration.c b/migration/migration.c
index b63ad91d34..14856cc930 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1772,6 +1772,13 @@ bool migration_in_postcopy_after_devices(MigrationState *s)
return migration_in_postcopy() && s->postcopy_after_devices;
}

+bool migration_in_incoming_postcopy(void)
+{
+ PostcopyState ps = postcopy_state_get();
+
+ return ps >= POSTCOPY_INCOMING_DISCARD && ps < POSTCOPY_INCOMING_END;
+}
+
bool migration_is_idle(void)
{
MigrationState *s = current_migration;
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;
--
2.25.4