[PATCH 3/8] virtio: categorize callbacks in GS

[Stefan Hajnoczi]

From: Emanuele Giuseppe Esposito <eesposit@redhat.com>

All the callbacks below are always running in the main loop.

The callbacks are the following:
- start/stop_ioeventfd: these are the callbacks where
  blk_set_aio_context(iothread) is done, so they are called in the main
  loop.

- save and load: called during migration, when VM is stopped from the
  main loop.

- reset: before calling this callback, stop_ioeventfd is invoked, so
  it can only run in the main loop.

- set_status: going through all the callers we can see it is called
  from a MemoryRegionOps callback, which always run in a vcpu thread and
  hold the BQL.

- realize: iothread is not even created yet.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220609143727.1151816-5-eesposit@redhat.com>
---
 hw/block/virtio-blk.c  | 2 ++
 hw/virtio/virtio-bus.c | 5 +++++
 hw/virtio/virtio-pci.c | 2 ++
 hw/virtio/virtio.c     | 8 ++++++++
 4 files changed, 17 insertions(+)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 96d00103a4..96bc11d2fe 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -1005,6 +1005,8 @@ static void virtio_blk_set_status(VirtIODevice *vdev, 
uint8_t status)
 {
     VirtIOBlock *s = VIRTIO_BLK(vdev);
 
+    GLOBAL_STATE_CODE();
+
     if (!(status & (VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK))) {
         assert(!s->dataplane_started);
     }
diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 896feb37a1..74cdf4bd27 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -23,6 +23,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/main-loop.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
 #include "qapi/error.h"
@@ -224,6 +225,8 @@ int virtio_bus_start_ioeventfd(VirtioBusState *bus)
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
     int r;
 
+    GLOBAL_STATE_CODE();
+
     if (!k->ioeventfd_assign || !k->ioeventfd_enabled(proxy)) {
         return -ENOSYS;
     }
@@ -248,6 +251,8 @@ void virtio_bus_stop_ioeventfd(VirtioBusState *bus)
     VirtIODevice *vdev;
     VirtioDeviceClass *vdc;
 
+    GLOBAL_STATE_CODE();
+
     if (!bus->ioeventfd_started) {
         return;
     }
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index a1c9dfa7bb..4f9a94f61b 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -313,6 +313,8 @@ static void virtio_ioport_write(void *opaque, uint32_t 
addr, uint32_t val)
     uint16_t vector;
     hwaddr pa;
 
+    GLOBAL_STATE_CODE();
+
     switch (addr) {
     case VIRTIO_PCI_GUEST_FEATURES:
         /* Guest does not negotiate properly?  We have to assume nothing. */
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 9683b2e158..468e8f5ad0 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2422,6 +2422,8 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
     trace_virtio_set_status(vdev, val);
 
+    GLOBAL_STATE_CODE();
+
     if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
         if (!(vdev->status & VIRTIO_CONFIG_S_FEATURES_OK) &&
             val & VIRTIO_CONFIG_S_FEATURES_OK) {
@@ -2515,6 +2517,8 @@ void virtio_reset(void *opaque)
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
     int i;
 
+    GLOBAL_STATE_CODE();
+
     virtio_set_status(vdev, 0);
     if (current_cpu) {
         /* Guest initiated reset */
@@ -3357,6 +3361,8 @@ int virtio_save(VirtIODevice *vdev, QEMUFile *f)
     uint32_t guest_features_lo = (vdev->guest_features & 0xffffffff);
     int i;
 
+    GLOBAL_STATE_CODE();
+
     if (k->save_config) {
         k->save_config(qbus->parent, f);
     }
@@ -3508,6 +3514,8 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int 
version_id)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
 
+    GLOBAL_STATE_CODE();
+
     /*
      * We poison the endianness to ensure it does not get used before
      * subsections have been loaded.
-- 
2.38.1