[PATCH V4 26/43] migration: close kvm after cpr

[Steve Sistare <steven.sistare@oracle.com>]

cpr-transfer breaks vfio network connectivity to and from the guest, and
the host system log shows:
  irq bypass consumer (token 00000000a03c32e5) registration fails: -16
which is EBUSY.  This occurs because KVM descriptors are still open in
the old QEMU process.  Close them.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 include/hw/vfio/vfio-device.h |  2 ++
 include/migration/cpr.h       |  2 ++
 include/system/kvm.h          |  1 +
 accel/kvm/kvm-all.c           | 28 ++++++++++++++++++++++++++++
 accel/stubs/kvm-stub.c        |  5 +++++
 hw/vfio/helpers.c             | 10 ++++++++++
 hw/vfio/vfio-stubs.c          | 13 +++++++++++++
 migration/cpr-transfer.c      | 18 ++++++++++++++++++
 migration/cpr.c               |  8 ++++++++
 migration/migration.c         |  1 +
 hw/vfio/meson.build           |  2 ++
 11 files changed, 90 insertions(+)
 create mode 100644 hw/vfio/vfio-stubs.c

diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
index 4e4d0b6..6eb6f21 100644
--- a/include/hw/vfio/vfio-device.h
+++ b/include/hw/vfio/vfio-device.h
@@ -231,4 +231,6 @@ void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp);
 void vfio_device_init(VFIODevice *vbasedev, int type, VFIODeviceOps *ops,
                       DeviceState *dev, bool ram_discard);
 int vfio_device_get_aw_bits(VFIODevice *vdev);
+
+void vfio_kvm_device_close(void);
 #endif /* HW_VFIO_VFIO_COMMON_H */
diff --git a/include/migration/cpr.h b/include/migration/cpr.h
index 07858e9..d09b657 100644
--- a/include/migration/cpr.h
+++ b/include/migration/cpr.h
@@ -32,7 +32,9 @@ void cpr_state_close(void);
 struct QIOChannel *cpr_state_ioc(void);
 
 bool cpr_incoming_needed(void *opaque);
+void cpr_kvm_close(void);
 
+void cpr_transfer_init(void);
 QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp);
 QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp);
 
diff --git a/include/system/kvm.h b/include/system/kvm.h
index b690dda..cfaa94c 100644
--- a/include/system/kvm.h
+++ b/include/system/kvm.h
@@ -194,6 +194,7 @@ bool kvm_has_sync_mmu(void);
 int kvm_has_vcpu_events(void);
 int kvm_max_nested_state_length(void);
 int kvm_has_gsi_routing(void);
+void kvm_close(void);
 
 /**
  * kvm_arm_supports_user_irq
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 278a506..d619448 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -512,16 +512,23 @@ static int do_kvm_destroy_vcpu(CPUState *cpu)
         goto err;
     }
 
+    /* If I am the CPU that created coalesced_mmio_ring, then discard it */
+    if (s->coalesced_mmio_ring == (void *)cpu->kvm_run + PAGE_SIZE) {
+        s->coalesced_mmio_ring = NULL;
+    }
+
     ret = munmap(cpu->kvm_run, mmap_size);
     if (ret < 0) {
         goto err;
     }
+    cpu->kvm_run = NULL;
 
     if (cpu->kvm_dirty_gfns) {
         ret = munmap(cpu->kvm_dirty_gfns, s->kvm_dirty_ring_bytes);
         if (ret < 0) {
             goto err;
         }
+        cpu->kvm_dirty_gfns = NULL;
     }
 
     kvm_park_vcpu(cpu);
@@ -600,6 +607,27 @@ err:
     return ret;
 }
 
+void kvm_close(void)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        cpu_remove_sync(cpu);
+        close(cpu->kvm_fd);
+        cpu->kvm_fd = -1;
+        close(cpu->kvm_vcpu_stats_fd);
+        cpu->kvm_vcpu_stats_fd = -1;
+    }
+
+    if (kvm_state && kvm_state->fd != -1) {
+        close(kvm_state->vmfd);
+        kvm_state->vmfd = -1;
+        close(kvm_state->fd);
+        kvm_state->fd = -1;
+    }
+    kvm_state = NULL;
+}
+
 /*
  * dirty pages logging control
  */
diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
index ecfd763..97dacb3 100644
--- a/accel/stubs/kvm-stub.c
+++ b/accel/stubs/kvm-stub.c
@@ -134,3 +134,8 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp)
 {
     return -ENOSYS;
 }
+
+void kvm_close(void)
+{
+    return;
+}
diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
index d0dbab1..af1db2f 100644
--- a/hw/vfio/helpers.c
+++ b/hw/vfio/helpers.c
@@ -117,6 +117,16 @@ bool vfio_get_info_dma_avail(struct vfio_iommu_type1_info *info,
 int vfio_kvm_device_fd = -1;
 #endif
 
+void vfio_kvm_device_close(void)
+{
+#ifdef CONFIG_KVM
+    if (vfio_kvm_device_fd != -1) {
+        close(vfio_kvm_device_fd);
+        vfio_kvm_device_fd = -1;
+    }
+#endif
+}
+
 int vfio_kvm_device_add_fd(int fd, Error **errp)
 {
 #ifdef CONFIG_KVM
diff --git a/hw/vfio/vfio-stubs.c b/hw/vfio/vfio-stubs.c
new file mode 100644
index 0000000..a4c8b56
--- /dev/null
+++ b/hw/vfio/vfio-stubs.c
@@ -0,0 +1,13 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/vfio/vfio-device.h"
+
+void vfio_kvm_device_close(void)
+{
+    return;
+}
diff --git a/migration/cpr-transfer.c b/migration/cpr-transfer.c
index e1f1403..396558f 100644
--- a/migration/cpr-transfer.c
+++ b/migration/cpr-transfer.c
@@ -17,6 +17,24 @@
 #include "migration/vmstate.h"
 #include "trace.h"
 
+static int cpr_transfer_notifier(NotifierWithReturn *notifier,
+                                 MigrationEvent *e,
+                                 Error **errp)
+{
+    if (e->type == MIG_EVENT_PRECOPY_DONE) {
+        cpr_kvm_close();
+    }
+    return 0;
+}
+
+void cpr_transfer_init(void)
+{
+    static NotifierWithReturn notifier;
+
+    migration_add_notifier_mode(&notifier, cpr_transfer_notifier,
+                                MIG_MODE_CPR_TRANSFER);
+}
+
 QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp)
 {
     MigrationAddress *addr = channel->addr;
diff --git a/migration/cpr.c b/migration/cpr.c
index a50a57e..49fb0a5 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -7,12 +7,14 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "hw/vfio/vfio-device.h"
 #include "migration/cpr.h"
 #include "migration/misc.h"
 #include "migration/options.h"
 #include "migration/qemu-file.h"
 #include "migration/savevm.h"
 #include "migration/vmstate.h"
+#include "system/kvm.h"
 #include "system/runstate.h"
 #include "trace.h"
 
@@ -264,3 +266,9 @@ bool cpr_incoming_needed(void *opaque)
     MigMode mode = migrate_mode();
     return mode == MIG_MODE_CPR_TRANSFER;
 }
+
+void cpr_kvm_close(void)
+{
+    kvm_close();
+    vfio_kvm_device_close();
+}
diff --git a/migration/migration.c b/migration/migration.c
index 4697732..89e2026 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -337,6 +337,7 @@ void migration_object_init(void)
 
     ram_mig_init();
     dirty_bitmap_mig_init();
+    cpr_transfer_init();
 
     /* Initialize cpu throttle timers */
     cpu_throttle_init();
diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
index 73d29f9..98134a7 100644
--- a/hw/vfio/meson.build
+++ b/hw/vfio/meson.build
@@ -17,6 +17,8 @@ vfio_ss.add(when: 'CONFIG_VFIO_IGD', if_true: files('igd.c'))
 
 specific_ss.add_all(when: 'CONFIG_VFIO', if_true: vfio_ss)
 
+system_ss.add(when: 'CONFIG_VFIO', if_false: files('vfio-stubs.c'))
+
 system_ss.add(when: 'CONFIG_VFIO_XGMAC', if_true: files('calxeda-xgmac.c'))
 system_ss.add(when: 'CONFIG_VFIO_AMD_XGBE', if_true: files('amd-xgbe.c'))
 system_ss.add(when: 'CONFIG_VFIO', if_true: files(
-- 
1.8.3.1