[PATCH QEMU HCI-8.1 v6 26/34] vfio/migration: don't assume the device is running on CPR incoming

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

Since the device descriptor is preserved across CPR, the device keeps
whatever state the source left it in, while vfio_migration_init() on
the target still caches RUNNING.  For a VM paused before CPR, the
device is in STOP, so on 'cont' vfio_migration_set_state() finds the
cached and the requested state equal and skips the ioctl: the guest
runs with a stopped device.

On CPR incoming, cache STOP instead, and have the VM state handler,
which doesn't touch the device during CPR, note where the VM leaves
it: RUNNING once the target starts the VM, STOP if it stays paused.
At CPR the device can only be in one of the two.

Fixes: c29a65ed685 ("vfio/container: preserve descriptors")
Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
---
 hw/vfio/migration.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index b142c9f2289..04d0de7cef0 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -914,6 +914,14 @@ static void vfio_vmstate_change(void *opaque, bool running, RunState state)
     Error *local_err = NULL;
     int ret;
 
+    /* CPR target only: the device kept its state, note where the VM left it */
+    if (cpr_is_incoming()) {
+        vbasedev->migration->device_state = running ?
+            VFIO_DEVICE_STATE_RUNNING : VFIO_DEVICE_STATE_STOP;
+        return;
+    }
+
+    /* CPR source only: the device keeps running across the exec */
     if (cpr_is_in_progress()) {
         return;
     }
@@ -1039,7 +1047,9 @@ static int vfio_migration_init(VFIODevice *vbasedev)
     vbasedev->migration = g_new0(VFIOMigration, 1);
     migration = vbasedev->migration;
     migration->vbasedev = vbasedev;
-    migration->device_state = VFIO_DEVICE_STATE_RUNNING;
+    /* A device inherited across CPR is in STOP unless the VM gets started */
+    migration->device_state = cpr_is_incoming() ? VFIO_DEVICE_STATE_STOP :
+                                                  VFIO_DEVICE_STATE_RUNNING;
     migration->data_fd = -1;
     migration->mig_flags = mig_flags;
 

-- 
2.47.1