[PATCH v3 0/6] hw/nvme: add basic live migration support

[PATCH v3 0/6] hw/nvme: add basic live migration support

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Dear friends,

This patchset adds basic live migration support for
QEMU emulated NVMe device.

Implementation has some limitations:
- only one NVMe namespace is supported
- SMART counters are not preserved
- CMB is not supported
- PMR is not supported
- SPDM is not supported
- SR-IOV is not supported

I believe this is something I can support in next patchset versions or
separately on-demand (when usecase appears).

Testing.

This patch series was manually tested on:
- Debian 13.3 VM (kernel 6.12.69+deb13-amd64) using fio on *non-root* NVMe disk
  (root disk was virtio-scsi):

time fio --name=nvme-verify \
    --filename=/dev/nvme0n1 \
    --size=5G \
    --rw=randwrite \
    --bs=4k \
    --iodepth=16 \
    --numjobs=1 \
    --direct=0 \
    --ioengine=io_uring \
    --verify=crc32c \
    --verify_fatal=1

- Windows Server 2022 VM (NVMe drive was a *root* disk) with opened browser
  playing video.

No defects were found.

I'm currently working to address feedback from Peter Xu and Klaus Jensen:
- improvements on migration API side to make dynamic arrays support more flexible
- figuring out what is a right way to go with NVMe feature migration capability checks

Changelog for version 3:
- rebased
- simple functional test was added (in accordance with Klaus Jensen's review comment)
  $ meson test 'func-x86_64-nvme_migration' --setup thorough -C build

Changelog for version 2:
- full support for AERs (in-flight requests and queued events too)

Kind regards,
Alex

Alexander Mikhalitsyn (6):
  migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC
  tests/functional/migration: add VM launch/configure hooks
  hw/nvme: add migration blockers for non-supported cases
  hw/nvme: split nvme_init_sq/nvme_init_cq into helpers
  hw/nvme: add basic live migration support
  tests/functional/x86_64: add migration test for NVMe device

 hw/nvme/ctrl.c                                | 665 +++++++++++++++++-
 hw/nvme/nvme.h                                |   5 +
 hw/nvme/trace-events                          |  11 +
 include/migration/vmstate.h                   |  33 +
 migration/vmstate-types.c                     |  88 +++
 tests/functional/migration.py                 |  22 +-
 tests/functional/x86_64/meson.build           |   1 +
 .../functional/x86_64/test_nvme_migration.py  | 159 +++++
 8 files changed, 951 insertions(+), 33 deletions(-)
 create mode 100755 tests/functional/x86_64/test_nvme_migration.py

-- 
2.47.3

[PATCH v3 1/6] migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC, which
helps to save/restore a dynamic array of pointers to
structures.

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
v2:
- added VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC
---
 include/migration/vmstate.h | 33 ++++++++++++++
 migration/vmstate-types.c   | 88 +++++++++++++++++++++++++++++++++++++
 2 files changed, 121 insertions(+)

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 89f9f49d20a..0bbe3317740 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -265,6 +265,7 @@ extern const VMStateInfo vmstate_info_bitmap;
 extern const VMStateInfo vmstate_info_qtailq;
 extern const VMStateInfo vmstate_info_gtree;
 extern const VMStateInfo vmstate_info_qlist;
+extern const VMStateInfo vmstate_info_ptrs_array_entry;
 
 #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0)
 /*
@@ -537,6 +538,38 @@ extern const VMStateInfo vmstate_info_qlist;
     .offset     = vmstate_offset_array(_s, _f, _type*, _n),          \
 }
 
+/*
+ * For migrating a dynamically allocated uint32-indexed array
+ * of pointers to structures (with NULL entries and with auto memory allocation).
+ *
+ * _type: type of structure pointed to
+ * _vmsd: VMSD for structure
+ * start: size of structure pointed to (for auto memory allocation)
+ */
+#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
+    .name       = (stringify(_field)),                                \
+    .version_id = (_version),                                         \
+    .num_offset = vmstate_offset_value(_state, _field_num, uint8_t), \
+    .info       = &vmstate_info_ptrs_array_entry,                     \
+    .vmsd       = &(_vmsd),                                           \
+    .start      = sizeof(_type),                                      \
+    .size       = sizeof(_type *),                                    \
+    .flags      = VMS_VARRAY_UINT8|VMS_POINTER,                      \
+    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
+}
+
+#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
+    .name       = (stringify(_field)),                                \
+    .version_id = (_version),                                         \
+    .num_offset = vmstate_offset_value(_state, _field_num, uint32_t), \
+    .info       = &vmstate_info_ptrs_array_entry,                     \
+    .vmsd       = &(_vmsd),                                           \
+    .start      = sizeof(_type),                                      \
+    .size       = sizeof(_type *),                                    \
+    .flags      = VMS_VARRAY_UINT32|VMS_POINTER,                      \
+    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
+}
+
 #define VMSTATE_VARRAY_OF_POINTER_UINT32(_field, _state, _field_num, _version, _info, _type) { \
     .name       = (stringify(_field)),                                    \
     .version_id = (_version),                                             \
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 89cb2114721..3335377cd07 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -942,3 +942,91 @@ const VMStateInfo vmstate_info_qlist = {
     .get  = get_qlist,
     .put  = put_qlist,
 };
+
+static int put_ptrs_array_entry(QEMUFile *f, void *ppv, size_t unused_size,
+                                const VMStateField *field, JSONWriter *vmdesc)
+{
+    const VMStateDescription *vmsd = field->vmsd;
+    int ret;
+    Error *local_err = NULL;
+    void *pv;
+
+    /*
+     * (ppv) is an address of an i-th element of a dynamic array.
+     *
+     * (ppv) can not be NULL unless we have some regression/bug in
+     * vmstate_save_state_v(), because it is result of pointer arithemic like:
+     * first_elem + size * i.
+     */
+    if (ppv == NULL) {
+        error_report("vmstate: put_ptrs_array_entry must be called with ppv != NULL");
+        return -EINVAL;
+    }
+
+    /* get a pointer to a structure */
+    pv = *(void **)ppv;
+
+    if (pv == NULL) {
+        /* write a mark telling that there was a NULL pointer */
+        qemu_put_byte(f, false);
+        return 0;
+    }
+
+    /* if pointer is not NULL, dump the structure contents with help of vmsd */
+    qemu_put_byte(f, true);
+    ret = vmstate_save_state(f, vmsd, pv, vmdesc, &local_err);
+    if (ret) {
+        error_report_err(local_err);
+        return ret;
+    }
+
+    return 0;
+}
+
+static int get_ptrs_array_entry(QEMUFile *f, void *ppv, size_t unused_size,
+                                const VMStateField *field)
+{
+    int ret = 0;
+    Error *local_err = NULL;
+    const VMStateDescription *vmsd = field->vmsd;
+    /* size of structure pointed to by elements of array */
+    size_t size = field->start;
+
+    if (ppv == NULL) {
+        error_report("vmstate: get_ptrs_array_entry must be called with ppv != NULL");
+        return -EINVAL;
+    }
+
+    /*
+     * We start from a clean array, all elements must be NULL, unless
+     * something we haven't prepared for has changed in vmstate_save_state_v().
+     * Let's check for this just in case.
+     */
+    if (*(void **)ppv != NULL) {
+        error_report("vmstate: get_ptrs_array_entry must be called with *ppv == NULL");
+        return -EINVAL;
+    }
+
+    if (qemu_get_byte(f)) {
+        void *pv;
+
+        /* allocate memory for structure */
+        pv = g_malloc0(size);
+        ret = vmstate_load_state(f, vmsd, pv, vmsd->version_id, &local_err);
+        if (ret) {
+            error_report_err(local_err);
+            g_free(pv);
+            return ret;
+        }
+
+        *(void **)ppv = pv;
+    }
+
+    return ret;
+}
+
+const VMStateInfo vmstate_info_ptrs_array_entry = {
+    .name = "ptrs_array_entry",
+    .get  = get_ptrs_array_entry,
+    .put  = put_ptrs_array_entry,
+};
-- 
2.47.3

[PATCH v3 2/6] tests/functional/migration: add VM launch/configure hooks

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Introduce configure_machine, launch_source_vm and assert_dest_vm
methods to allow child classes to override some pieces of
source/dest VMs creation, start and check logic.

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
---
 tests/functional/migration.py | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/tests/functional/migration.py b/tests/functional/migration.py
index 2bfb1f77901..759906fd820 100644
--- a/tests/functional/migration.py
+++ b/tests/functional/migration.py
@@ -41,17 +41,33 @@ def assert_migration(self, src_vm, dst_vm):
         self.assertEqual(dst_vm.cmd('query-status')['status'], 'running')
         self.assertEqual(src_vm.cmd('query-status')['status'],'postmigrate')
 
+    # Can be overridden by subclasses to configure both source/dest VMs.
+    def configure_machine(self, vm):
+        vm.add_args('-nodefaults')
+
+    # Can be overridden by subclasses to prepare the source VM before migration,
+    # e.g. by running some workload inside the source VM to see if it continues
+    # to run properly after migration.
+    def launch_source_vm(self, vm):
+        vm.launch()
+
+    # Can be overridden by subclasses to check the destination VM after migration,
+    # e.g. by checking if the workload is still running after migration.
+    def assert_dest_vm(self, vm):
+        pass
+
     def do_migrate(self, dest_uri, src_uri=None):
         dest_vm = self.get_vm('-incoming', dest_uri, name="dest-qemu")
-        dest_vm.add_args('-nodefaults')
+        self.configure_machine(dest_vm)
         dest_vm.launch()
         if src_uri is None:
             src_uri = dest_uri
         source_vm = self.get_vm(name="source-qemu")
-        source_vm.add_args('-nodefaults')
-        source_vm.launch()
+        self.configure_machine(source_vm)
+        self.launch_source_vm(source_vm)
         source_vm.qmp('migrate', uri=src_uri)
         self.assert_migration(source_vm, dest_vm)
+        self.assert_dest_vm(dest_vm)
 
     def _get_free_port(self, ports):
         port = ports.find_free_port()
-- 
2.47.3

[PATCH v3 3/6] hw/nvme: add migration blockers for non-supported cases

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Let's block migration for cases we don't support:
- SR-IOV
- CMB
- PMR
- SPDM

No functional changes here, because NVMe migration is
not supported at all as of this commit.

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
---
 hw/nvme/ctrl.c | 35 +++++++++++++++++++++++++++++++++++
 hw/nvme/nvme.h |  3 +++
 2 files changed, 38 insertions(+)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index cc4593cd427..4694bdb4d02 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -207,6 +207,7 @@
 #include "hw/pci/msix.h"
 #include "hw/pci/pcie_sriov.h"
 #include "system/spdm-socket.h"
+#include "migration/blocker.h"
 #include "migration/vmstate.h"
 
 #include "nvme.h"
@@ -8962,6 +8963,14 @@ static bool nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, Error **errp)
     pcie_endpoint_cap_init(pci_dev, 0x80);
     pcie_cap_flr_init(pci_dev);
     if (n->params.sriov_max_vfs) {
+        if (n->migration_blocker == NULL) {
+            error_setg(&n->migration_blocker,
+                       "Migration is disabled when SR-IOV capability is set");
+            if (migrate_add_blocker(&n->migration_blocker, errp) < 0) {
+                return false;
+            }
+        }
+
         pcie_ari_init(pci_dev, 0x100);
     }
 
@@ -9025,6 +9034,14 @@ static bool nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, Error **errp)
     if (pci_dev->spdm_port) {
         uint16_t doe_offset = PCI_CONFIG_SPACE_SIZE;
 
+        if (n->migration_blocker == NULL) {
+            error_setg(&n->migration_blocker,
+                       "Migration is disabled when SPDM responder is used");
+            if (migrate_add_blocker(&n->migration_blocker, errp) < 0) {
+                return false;
+            }
+        }
+
         switch  (pci_dev->spdm_trans) {
         case SPDM_SOCKET_TRANSPORT_TYPE_PCI_DOE:
             if (n->params.sriov_max_vfs) {
@@ -9053,10 +9070,26 @@ static bool nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, Error **errp)
     }
 
     if (n->params.cmb_size_mb) {
+        if (n->migration_blocker == NULL) {
+            error_setg(&n->migration_blocker,
+                       "Migration is disabled when CMB feature is used");
+            if (migrate_add_blocker(&n->migration_blocker, errp) < 0) {
+                return false;
+            }
+        }
+
         nvme_init_cmb(n, pci_dev);
     }
 
     if (n->pmr.dev) {
+        if (n->migration_blocker == NULL) {
+            error_setg(&n->migration_blocker,
+                       "Migration is disabled when PMR feature is used");
+            if (migrate_add_blocker(&n->migration_blocker, errp) < 0) {
+                return false;
+            }
+        }
+
         if (!nvme_init_pmr(n, pci_dev, errp)) {
             return false;
         }
@@ -9365,6 +9398,8 @@ static void nvme_exit(PCIDevice *pci_dev)
     }
 
     memory_region_del_subregion(&n->bar0, &n->iomem);
+
+    migrate_del_blocker(&n->migration_blocker);
 }
 
 static const Property nvme_props[] = {
diff --git a/hw/nvme/nvme.h b/hw/nvme/nvme.h
index d66f7dc82d5..457b6637249 100644
--- a/hw/nvme/nvme.h
+++ b/hw/nvme/nvme.h
@@ -666,6 +666,9 @@ typedef struct NvmeCtrl {
 
     /* Socket mapping to SPDM over NVMe Security In/Out commands */
     int spdm_socket;
+
+    /* Migration-related stuff */
+    Error *migration_blocker;
 } NvmeCtrl;
 
 typedef enum NvmeResetType {
-- 
2.47.3

[PATCH v3 4/6] hw/nvme: split nvme_init_sq/nvme_init_cq into helpers

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
---
 hw/nvme/ctrl.c | 57 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 36 insertions(+), 21 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 4694bdb4d02..89cc26d745b 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -4852,18 +4852,14 @@ static uint16_t nvme_del_sq(NvmeCtrl *n, NvmeRequest *req)
     return NVME_SUCCESS;
 }
 
-static void nvme_init_sq(NvmeSQueue *sq, NvmeCtrl *n, uint64_t dma_addr,
-                         uint16_t sqid, uint16_t cqid, uint16_t size)
+static void __nvme_init_sq(NvmeSQueue *sq)
 {
+    NvmeCtrl *n = sq->ctrl;
+    uint16_t sqid = sq->sqid;
+    uint16_t cqid = sq->cqid;
     int i;
     NvmeCQueue *cq;
 
-    sq->ctrl = n;
-    sq->dma_addr = dma_addr;
-    sq->sqid = sqid;
-    sq->size = size;
-    sq->cqid = cqid;
-    sq->head = sq->tail = 0;
     sq->io_req = g_new0(NvmeRequest, sq->size);
 
     QTAILQ_INIT(&sq->req_list);
@@ -4893,6 +4889,18 @@ static void nvme_init_sq(NvmeSQueue *sq, NvmeCtrl *n, uint64_t dma_addr,
     n->sq[sqid] = sq;
 }
 
+static void nvme_init_sq(NvmeSQueue *sq, NvmeCtrl *n, uint64_t dma_addr,
+                         uint16_t sqid, uint16_t cqid, uint16_t size)
+{
+    sq->ctrl = n;
+    sq->dma_addr = dma_addr;
+    sq->sqid = sqid;
+    sq->size = size;
+    sq->cqid = cqid;
+    sq->head = sq->tail = 0;
+    __nvme_init_sq(sq);
+}
+
 static uint16_t nvme_create_sq(NvmeCtrl *n, NvmeRequest *req)
 {
     NvmeSQueue *sq;
@@ -5553,24 +5561,16 @@ static uint16_t nvme_del_cq(NvmeCtrl *n, NvmeRequest *req)
     return NVME_SUCCESS;
 }
 
-static void nvme_init_cq(NvmeCQueue *cq, NvmeCtrl *n, uint64_t dma_addr,
-                         uint16_t cqid, uint16_t vector, uint16_t size,
-                         uint16_t irq_enabled)
+static void __nvme_init_cq(NvmeCQueue *cq)
 {
+    NvmeCtrl *n = cq->ctrl;
     PCIDevice *pci = PCI_DEVICE(n);
+    uint16_t cqid = cq->cqid;
 
-    if (msix_enabled(pci) && irq_enabled) {
-        msix_vector_use(pci, vector);
+    if (msix_enabled(pci) && cq->irq_enabled) {
+        msix_vector_use(pci, cq->vector);
     }
 
-    cq->ctrl = n;
-    cq->cqid = cqid;
-    cq->size = size;
-    cq->dma_addr = dma_addr;
-    cq->phase = 1;
-    cq->irq_enabled = irq_enabled;
-    cq->vector = vector;
-    cq->head = cq->tail = 0;
     QTAILQ_INIT(&cq->req_list);
     QTAILQ_INIT(&cq->sq_list);
     if (n->dbbuf_enabled) {
@@ -5588,6 +5588,21 @@ static void nvme_init_cq(NvmeCQueue *cq, NvmeCtrl *n, uint64_t dma_addr,
                                  &DEVICE(cq->ctrl)->mem_reentrancy_guard);
 }
 
+static void nvme_init_cq(NvmeCQueue *cq, NvmeCtrl *n, uint64_t dma_addr,
+                         uint16_t cqid, uint16_t vector, uint16_t size,
+                         uint16_t irq_enabled)
+{
+    cq->ctrl = n;
+    cq->cqid = cqid;
+    cq->size = size;
+    cq->dma_addr = dma_addr;
+    cq->phase = 1;
+    cq->irq_enabled = irq_enabled;
+    cq->vector = vector;
+    cq->head = cq->tail = 0;
+    __nvme_init_cq(cq);
+}
+
 static uint16_t nvme_create_cq(NvmeCtrl *n, NvmeRequest *req)
 {
     NvmeCQueue *cq;
-- 
2.47.3

[PATCH v3 5/6] hw/nvme: add basic live migration support

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

It has some limitations:
- only one NVMe namespace is supported
- SMART counters are not preserved
- CMB is not supported
- PMR is not supported
- SPDM is not supported
- SR-IOV is not supported

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
v2:
- AERs are now fully supported
---
 hw/nvme/ctrl.c       | 573 ++++++++++++++++++++++++++++++++++++++++++-
 hw/nvme/nvme.h       |   2 +
 hw/nvme/trace-events |  11 +
 3 files changed, 577 insertions(+), 9 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 89cc26d745b..cdfda1d3be8 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -208,6 +208,7 @@
 #include "hw/pci/pcie_sriov.h"
 #include "system/spdm-socket.h"
 #include "migration/blocker.h"
+#include "migration/qemu-file-types.h"
 #include "migration/vmstate.h"
 
 #include "nvme.h"
@@ -4901,6 +4902,25 @@ static void nvme_init_sq(NvmeSQueue *sq, NvmeCtrl *n, uint64_t dma_addr,
     __nvme_init_sq(sq);
 }
 
+static void nvme_restore_sq(NvmeSQueue *sq_from)
+{
+    NvmeCtrl *n = sq_from->ctrl;
+    NvmeSQueue *sq = sq_from;
+
+    if (sq_from->sqid == 0) {
+        sq = &n->admin_sq;
+        sq->ctrl = n;
+        sq->dma_addr = sq_from->dma_addr;
+        sq->sqid = sq_from->sqid;
+        sq->size = sq_from->size;
+        sq->cqid = sq_from->cqid;
+        sq->head = sq_from->head;
+        sq->tail = sq_from->tail;
+    }
+
+    __nvme_init_sq(sq);
+}
+
 static uint16_t nvme_create_sq(NvmeCtrl *n, NvmeRequest *req)
 {
     NvmeSQueue *sq;
@@ -5603,6 +5623,27 @@ static void nvme_init_cq(NvmeCQueue *cq, NvmeCtrl *n, uint64_t dma_addr,
     __nvme_init_cq(cq);
 }
 
+static void nvme_restore_cq(NvmeCQueue *cq_from)
+{
+    NvmeCtrl *n = cq_from->ctrl;
+    NvmeCQueue *cq = cq_from;
+
+    if (cq_from->cqid == 0) {
+        cq = &n->admin_cq;
+        cq->ctrl = n;
+        cq->cqid = cq_from->cqid;
+        cq->size = cq_from->size;
+        cq->dma_addr = cq_from->dma_addr;
+        cq->phase = cq_from->phase;
+        cq->irq_enabled = cq_from->irq_enabled;
+        cq->vector = cq_from->vector;
+        cq->head = cq_from->head;
+        cq->tail = cq_from->tail;
+    }
+
+    __nvme_init_cq(cq);
+}
+
 static uint16_t nvme_create_cq(NvmeCtrl *n, NvmeRequest *req)
 {
     NvmeCQueue *cq;
@@ -7291,7 +7332,7 @@ static uint16_t nvme_dbbuf_config(NvmeCtrl *n, const NvmeRequest *req)
     n->dbbuf_eis = eis_addr;
     n->dbbuf_enabled = true;
 
-    for (i = 0; i < n->params.max_ioqpairs + 1; i++) {
+    for (i = 0; i < n->num_queues; i++) {
         NvmeSQueue *sq = n->sq[i];
         NvmeCQueue *cq = n->cq[i];
 
@@ -7731,7 +7772,7 @@ static int nvme_atomic_write_check(NvmeCtrl *n, NvmeCmd *cmd,
     /*
      * Walk the queues to see if there are any atomic conflicts.
      */
-    for (i = 1; i < n->params.max_ioqpairs + 1; i++) {
+    for (i = 1; i < n->num_queues; i++) {
         NvmeSQueue *sq;
         NvmeRequest *req;
         NvmeRwCmd *req_rw;
@@ -7801,6 +7842,10 @@ static void nvme_process_sq(void *opaque)
     NvmeCmd cmd;
     NvmeRequest *req;
 
+    if (qatomic_read(&n->stop_processing_sq)) {
+        return;
+    }
+
     if (n->dbbuf_enabled) {
         nvme_update_sq_tail(sq);
     }
@@ -7809,6 +7854,10 @@ static void nvme_process_sq(void *opaque)
         NvmeAtomic *atomic;
         bool cmd_is_atomic;
 
+        if (qatomic_read(&n->stop_processing_sq)) {
+            return;
+        }
+
         addr = sq->dma_addr + (sq->head << NVME_SQES);
         if (nvme_addr_read(n, addr, (void *)&cmd, sizeof(cmd))) {
             trace_pci_nvme_err_addr_read(addr);
@@ -7917,12 +7966,12 @@ static void nvme_ctrl_reset(NvmeCtrl *n, NvmeResetType rst)
         nvme_ns_drain(ns);
     }
 
-    for (i = 0; i < n->params.max_ioqpairs + 1; i++) {
+    for (i = 0; i < n->num_queues; i++) {
         if (n->sq[i] != NULL) {
             nvme_free_sq(n->sq[i], n);
         }
     }
-    for (i = 0; i < n->params.max_ioqpairs + 1; i++) {
+    for (i = 0; i < n->num_queues; i++) {
         if (n->cq[i] != NULL) {
             nvme_free_cq(n->cq[i], n);
         }
@@ -8592,6 +8641,8 @@ static bool nvme_check_params(NvmeCtrl *n, Error **errp)
         params->max_ioqpairs = params->num_queues - 1;
     }
 
+    n->num_queues = params->max_ioqpairs + 1;
+
     if (n->namespace.blkconf.blk && n->subsys) {
         error_setg(errp, "subsystem support is unavailable with legacy "
                    "namespace ('drive' property)");
@@ -8746,8 +8797,8 @@ static void nvme_init_state(NvmeCtrl *n)
         n->conf_msix_qsize = n->params.msix_qsize;
     }
 
-    n->sq = g_new0(NvmeSQueue *, n->params.max_ioqpairs + 1);
-    n->cq = g_new0(NvmeCQueue *, n->params.max_ioqpairs + 1);
+    n->sq = g_new0(NvmeSQueue *, n->num_queues);
+    n->cq = g_new0(NvmeCQueue *, n->num_queues);
     n->temperature = NVME_TEMPERATURE;
     n->features.temp_thresh_hi = NVME_TEMPERATURE_WARNING;
     n->starttime_ms = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
@@ -8990,7 +9041,7 @@ static bool nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, Error **errp)
     }
 
     if (n->params.msix_exclusive_bar && !pci_is_vf(pci_dev)) {
-        bar_size = nvme_mbar_size(n->params.max_ioqpairs + 1, 0, NULL, NULL);
+        bar_size = nvme_mbar_size(n->num_queues, 0, NULL, NULL);
         memory_region_init_io(&n->iomem, OBJECT(n), &nvme_mmio_ops, n, "nvme",
                               bar_size);
         pci_register_bar(pci_dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY |
@@ -9002,7 +9053,7 @@ static bool nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, Error **errp)
         /* add one to max_ioqpairs to account for the admin queue pair */
         if (!pci_is_vf(pci_dev)) {
             nr_vectors = n->params.msix_qsize;
-            bar_size = nvme_mbar_size(n->params.max_ioqpairs + 1,
+            bar_size = nvme_mbar_size(n->num_queues,
                                       nr_vectors, &msix_table_offset,
                                       &msix_pba_offset);
         } else {
@@ -9552,9 +9603,513 @@ static uint32_t nvme_pci_read_config(PCIDevice *dev, uint32_t address, int len)
     return pci_default_read_config(dev, address, len);
 }
 
+static bool nvme_ctrl_pre_save(void *opaque, Error **errp)
+{
+    NvmeCtrl *n = opaque;
+    int i;
+
+    trace_pci_nvme_pre_save_enter(n);
+
+    /* ask SQ processing code not to take new requests */
+    qatomic_set(&n->stop_processing_sq, true);
+
+    /* prevent new in-flight IO from appearing */
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeSQueue *sq = n->sq[i];
+
+        if (!sq)
+            continue;
+
+        qemu_bh_cancel(sq->bh);
+    }
+
+    /* drain all IO */
+    for (i = 1; i <= NVME_MAX_NAMESPACES; i++) {
+        NvmeNamespace *ns;
+
+        ns = nvme_ns(n, i);
+        if (!ns) {
+            continue;
+        }
+
+        trace_pci_nvme_pre_save_ns_drain(n, i);
+        nvme_ns_drain(ns);
+    }
+
+    /*
+     * Now, we should take care of AERs.
+     *
+     * 1. Save all queued events (n->aer_queue).
+     *    This is done automatically, see nvme_vmstate VMStateDescription.
+     *    Here we only need to print them for debugging purpose.
+     * 2. Go over outstanding AER requests (n->aer_reqs) and check they are
+     *    all have expected opcode (NVME_ADM_CMD_ASYNC_EV_REQ) and other fields.
+     *
+     * We must be really careful here, because in case of further QEMU NVMe changes,
+     * we may break migration without noticing it, or worse, introduce silent
+     * data corruption during migration.
+     */
+    if (n->aer_queued) {
+        NvmeAsyncEvent *event;
+
+        QTAILQ_FOREACH(event, &n->aer_queue, entry) {
+            trace_pci_nvme_pre_save_aer(event->result.event_type, event->result.event_info,
+                                        event->result.log_page);
+        }
+    }
+
+    for (i = 0; i < n->outstanding_aers; i++) {
+        NvmeRequest *re = n->aer_reqs[i];
+
+        /*
+         * Can't use assert() here, because we don't want
+         * to just crash QEMU when user requests a migration.
+         */
+        if (!(re->cmd.opcode == NVME_ADM_CMD_ASYNC_EV_REQ)) {
+            error_setg(errp, "re->cmd.opcode (%u) != NVME_ADM_CMD_ASYNC_EV_REQ", re->cmd.opcode);
+            goto err;
+        }
+
+        if (!(re->ns == NULL)) {
+            error_setg(errp, "re->ns != NULL");
+            goto err;
+        }
+
+        if (!(re->sq == &n->admin_sq)) {
+            error_setg(errp, "re->sq != &n->admin_sq");
+            goto err;
+        }
+
+        if (!(re->aiocb == NULL)) {
+            error_setg(errp, "re->aiocb != NULL");
+            goto err;
+        }
+
+        if (!(re->opaque == NULL)) {
+            error_setg(errp, "re->opaque != NULL");
+            goto err;
+        }
+
+        if (!(re->atomic_write == false)) {
+            error_setg(errp, "re->atomic_write != false");
+            goto err;
+        }
+
+        if (re->sg.flags & NVME_SG_ALLOC) {
+            error_setg(errp, "unexpected NVME_SG_ALLOC flag in re->sg.flags");
+            goto err;
+        }
+    }
+
+    /* wait when all in-flight IO requests (except NVME_ADM_CMD_ASYNC_EV_REQ) are processed */
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeRequest *req;
+        NvmeSQueue *sq = n->sq[i];
+
+        if (!sq)
+            continue;
+
+        trace_pci_nvme_pre_save_sq_out_req_drain_wait(n, i, sq->head, sq->tail, sq->size);
+
+wait_out_reqs:
+        QTAILQ_FOREACH(req, &sq->out_req_list, entry) {
+            if (req->cmd.opcode != NVME_ADM_CMD_ASYNC_EV_REQ) {
+                cpu_relax();
+                goto wait_out_reqs;
+            }
+        }
+
+        trace_pci_nvme_pre_save_sq_out_req_drain_wait_end(n, i, sq->head, sq->tail);
+    }
+
+    /* wait when all IO requests completions are written to guest memory */
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeCQueue *cq = n->cq[i];
+
+        if (!cq)
+            continue;
+
+        trace_pci_nvme_pre_save_cq_req_drain_wait(n, i, cq->head, cq->tail, cq->size);
+
+        while (!QTAILQ_EMPTY(&cq->req_list)) {
+            /*
+             * nvme_post_cqes() can't do its job of cleaning cq->req_list
+             * when CQ is full, it means that we need to save what we have in
+             * cq->req_list and restore it back on VM resume.
+             *
+             * Good thing is that this can only happen when guest hasn't
+             * processed CQ for a long time and at the same time, many SQEs
+             * are in flight.
+             *
+             * For now, let's just block migration in this rare case.
+             */
+            if (nvme_cq_full(cq)) {
+                error_setg(errp, "no free space in CQ (not supported)");
+                goto err;
+            }
+
+            cpu_relax();
+        }
+
+        trace_pci_nvme_pre_save_cq_req_drain_wait_end(n, i, cq->head, cq->tail);
+    }
+
+    for (uint32_t nsid = 0; nsid <= NVME_MAX_NAMESPACES; nsid++) {
+        NvmeNamespace *ns = n->namespaces[nsid];
+
+        if (!ns)
+            continue;
+
+        if (ns != &n->namespace) {
+            error_setg(errp, "only one NVMe namespace is supported for migration");
+            goto err;
+        }
+    }
+
+    return true;
+
+err:
+    /* restore sq processing back to normal */
+    qatomic_set(&n->stop_processing_sq, false);
+    return false;
+}
+
+static bool nvme_ctrl_post_load(void *opaque, int version_id, Error **errp)
+{
+    NvmeCtrl *n = opaque;
+    int i;
+
+    trace_pci_nvme_post_load_enter(n);
+
+    /* restore CQs first */
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeCQueue *cq = n->cq[i];
+
+        if (!cq)
+            continue;
+
+        cq->ctrl = n;
+        nvme_restore_cq(cq);
+        trace_pci_nvme_post_load_restore_cq(n, i, cq->head, cq->tail, cq->size);
+
+        if (i == 0) {
+            /*
+             * Admin CQ lives in n->admin_cq, we don't need
+             * memory allocated for it in get_ptrs_array_entry() anymore.
+             *
+             * nvme_restore_cq() also takes care of:
+             * n->cq[0] = &n->admin_cq;
+             * so n->cq[0] remains valid.
+             */
+            g_free(cq);
+        }
+    }
+
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeSQueue *sq = n->sq[i];
+
+        if (!sq)
+            continue;
+
+        sq->ctrl = n;
+        nvme_restore_sq(sq);
+        trace_pci_nvme_post_load_restore_sq(n, i, sq->head, sq->tail, sq->size);
+
+        if (i == 0) {
+            /* same as for CQ */
+            g_free(sq);
+        }
+    }
+
+    if (n->aer_queued) {
+        NvmeAsyncEvent *event;
+
+        QTAILQ_FOREACH(event, &n->aer_queue, entry) {
+            trace_pci_nvme_post_load_aer(event->result.event_type, event->result.event_info,
+                                         event->result.log_page);
+        }
+    }
+
+    for (i = 0; i < n->outstanding_aers; i++) {
+        NvmeSQueue *sq = &n->admin_sq;
+        NvmeRequest *req_from = n->aer_reqs[i];
+        NvmeRequest *req;
+
+        /*
+         * We use nvme_vmstate VMStateDescription to save/restore
+         * NvmeRequest structures, but tricky thing here is that
+         * memory for each n->aer_reqs[i] will be allocated separately
+         * during restore. It doesn't work for us. We need to take
+         * an existing NvmeRequest structure from SQ's req_list
+         * and fill it with data from the newly allocated one (req_from).
+         * Then, we can safely release allocated memory for it.
+         */
+
+        /* take an NvmeRequest struct from SQ */
+        req = QTAILQ_FIRST(&sq->req_list);
+        QTAILQ_REMOVE(&sq->req_list, req, entry);
+        QTAILQ_INSERT_TAIL(&sq->out_req_list, req, entry);
+        nvme_req_clear(req);
+
+        /* copy data from the source NvmeRequest */
+        req->status = req_from->status;
+        memcpy(&req->cqe, &req_from->cqe, sizeof(NvmeCqe));
+        memcpy(&req->cmd, &req_from->cmd, sizeof(NvmeCmd));
+
+        n->aer_reqs[i] = req;
+        g_free(req_from);
+    }
+
+    /*
+     * We need to attach namespaces (currently, only one namespace is
+     * supported for migration).
+     * This logic comes from nvme_start_ctrl().
+     */
+    for (i = 1; i <= NVME_MAX_NAMESPACES; i++) {
+        NvmeNamespace *ns = nvme_subsys_ns(n->subsys, i);
+
+        if (!ns || (!ns->params.shared && ns->ctrl != n)) {
+            continue;
+        }
+
+        if (nvme_csi_supported(n, ns->csi) && !ns->params.detached) {
+            if (!ns->attached || ns->params.shared) {
+                nvme_attach_ns(n, ns);
+            }
+        }
+    }
+
+    /* schedule SQ processing */
+    for (i = 0; i < n->num_queues; i++) {
+        NvmeSQueue *sq = n->sq[i];
+
+        if (!sq)
+            continue;
+
+        qemu_bh_schedule(sq->bh);
+    }
+
+    /*
+     * We ensured in pre_save() that cq->req_list was empty,
+     * so we don't need to schedule BH for CQ processing.
+     */
+
+    return true;
+}
+
+static const VMStateDescription nvme_vmstate_bar = {
+    .name = "nvme-bar",
+    .minimum_version_id = 1,
+    .version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT64(cap, NvmeBar),
+        VMSTATE_UINT32(vs, NvmeBar),
+        VMSTATE_UINT32(intms, NvmeBar),
+        VMSTATE_UINT32(intmc, NvmeBar),
+        VMSTATE_UINT32(cc, NvmeBar),
+        VMSTATE_UINT8_ARRAY(rsvd24, NvmeBar, 4),
+        VMSTATE_UINT32(csts, NvmeBar),
+        VMSTATE_UINT32(nssr, NvmeBar),
+        VMSTATE_UINT32(aqa, NvmeBar),
+        VMSTATE_UINT64(asq, NvmeBar),
+        VMSTATE_UINT64(acq, NvmeBar),
+        VMSTATE_UINT32(cmbloc, NvmeBar),
+        VMSTATE_UINT32(cmbsz, NvmeBar),
+        VMSTATE_UINT32(bpinfo, NvmeBar),
+        VMSTATE_UINT32(bprsel, NvmeBar),
+        VMSTATE_UINT64(bpmbl, NvmeBar),
+        VMSTATE_UINT64(cmbmsc, NvmeBar),
+        VMSTATE_UINT32(cmbsts, NvmeBar),
+        VMSTATE_UINT8_ARRAY(rsvd92, NvmeBar, 3492),
+        VMSTATE_UINT32(pmrcap, NvmeBar),
+        VMSTATE_UINT32(pmrctl, NvmeBar),
+        VMSTATE_UINT32(pmrsts, NvmeBar),
+        VMSTATE_UINT32(pmrebs, NvmeBar),
+        VMSTATE_UINT32(pmrswtp, NvmeBar),
+        VMSTATE_UINT32(pmrmscl, NvmeBar),
+        VMSTATE_UINT32(pmrmscu, NvmeBar),
+        VMSTATE_UINT8_ARRAY(css, NvmeBar, 484),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+static const VMStateDescription nvme_vmstate_cqueue = {
+    .name = "nvme-cq",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT8(phase, NvmeCQueue),
+        VMSTATE_UINT16(cqid, NvmeCQueue),
+        VMSTATE_UINT16(irq_enabled, NvmeCQueue),
+        VMSTATE_UINT32(head, NvmeCQueue),
+        VMSTATE_UINT32(tail, NvmeCQueue),
+        VMSTATE_UINT32(vector, NvmeCQueue),
+        VMSTATE_UINT32(size, NvmeCQueue),
+        VMSTATE_UINT64(dma_addr, NvmeCQueue),
+        /* db_addr, ei_addr, etc will be recalculated */
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_squeue = {
+    .name = "nvme-sq",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT16(sqid, NvmeSQueue),
+        VMSTATE_UINT16(cqid, NvmeSQueue),
+        VMSTATE_UINT32(head, NvmeSQueue),
+        VMSTATE_UINT32(tail, NvmeSQueue),
+        VMSTATE_UINT32(size, NvmeSQueue),
+        VMSTATE_UINT64(dma_addr, NvmeSQueue),
+        /* db_addr, ei_addr, etc will be recalculated */
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_async_event_result = {
+    .name = "nvme-async-event-result",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT8(event_type, NvmeAerResult),
+        VMSTATE_UINT8(event_info, NvmeAerResult),
+        VMSTATE_UINT8(log_page, NvmeAerResult),
+        VMSTATE_UINT8(resv, NvmeAerResult),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_async_event = {
+    .name = "nvme-async-event",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_STRUCT(result, NvmeAsyncEvent, 0, nvme_vmstate_async_event_result, NvmeAerResult),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_cqe = {
+    .name = "nvme-cqe",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT32(result, NvmeCqe),
+        VMSTATE_UINT32(dw1, NvmeCqe),
+        VMSTATE_UINT16(sq_head, NvmeCqe),
+        VMSTATE_UINT16(sq_id, NvmeCqe),
+        VMSTATE_UINT16(cid, NvmeCqe),
+        VMSTATE_UINT16(status, NvmeCqe),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_cmd_dptr_sgl = {
+    .name = "nvme-request-cmd-dptr-sgl",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT64(addr, NvmeSglDescriptor),
+        VMSTATE_UINT32(len, NvmeSglDescriptor),
+        VMSTATE_UINT8_ARRAY(rsvd, NvmeSglDescriptor, 3),
+        VMSTATE_UINT8(type, NvmeSglDescriptor),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_cmd_dptr = {
+    .name = "nvme-request-cmd-dptr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT64(prp1, NvmeCmdDptr),
+        VMSTATE_UINT64(prp2, NvmeCmdDptr),
+        VMSTATE_STRUCT(sgl, NvmeCmdDptr, 0, nvme_vmstate_cmd_dptr_sgl, NvmeSglDescriptor),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_cmd = {
+    .name = "nvme-request-cmd",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT8(opcode, NvmeCmd),
+        VMSTATE_UINT8(flags, NvmeCmd),
+        VMSTATE_UINT16(cid, NvmeCmd),
+        VMSTATE_UINT32(nsid, NvmeCmd),
+        VMSTATE_UINT64(res1, NvmeCmd),
+        VMSTATE_UINT64(mptr, NvmeCmd),
+        VMSTATE_STRUCT(dptr, NvmeCmd, 0, nvme_vmstate_cmd_dptr, NvmeCmdDptr),
+        VMSTATE_UINT32(cdw10, NvmeCmd),
+        VMSTATE_UINT32(cdw11, NvmeCmd),
+        VMSTATE_UINT32(cdw12, NvmeCmd),
+        VMSTATE_UINT32(cdw13, NvmeCmd),
+        VMSTATE_UINT32(cdw14, NvmeCmd),
+        VMSTATE_UINT32(cdw15, NvmeCmd),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription nvme_vmstate_request = {
+    .name = "nvme-request",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT16(status, NvmeRequest),
+        VMSTATE_STRUCT(cqe, NvmeRequest, 0, nvme_vmstate_cqe, NvmeCqe),
+        VMSTATE_STRUCT(cmd, NvmeRequest, 0, nvme_vmstate_cmd, NvmeCmd),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription nvme_vmstate = {
     .name = "nvme",
-    .unmigratable = 1,
+    .minimum_version_id = 1,
+    .version_id = 1,
+    .pre_save_errp = nvme_ctrl_pre_save,
+    .post_load_errp = nvme_ctrl_post_load,
+    .fields = (const VMStateField[]) {
+        VMSTATE_PCI_DEVICE(parent_obj, NvmeCtrl),
+        VMSTATE_MSIX(parent_obj, NvmeCtrl),
+        VMSTATE_STRUCT(bar, NvmeCtrl, 0, nvme_vmstate_bar, NvmeBar),
+
+        VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(
+            sq, NvmeCtrl, num_queues, 0, nvme_vmstate_squeue, NvmeSQueue),
+        VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(
+            cq, NvmeCtrl, num_queues, 0, nvme_vmstate_cqueue, NvmeCQueue),
+
+        VMSTATE_BOOL(qs_created, NvmeCtrl),
+        VMSTATE_UINT32(page_size, NvmeCtrl),
+        VMSTATE_UINT16(page_bits, NvmeCtrl),
+        VMSTATE_UINT16(max_prp_ents, NvmeCtrl),
+        VMSTATE_UINT32(max_q_ents, NvmeCtrl),
+        VMSTATE_UINT8(outstanding_aers, NvmeCtrl),
+        VMSTATE_UINT32(irq_status, NvmeCtrl),
+        VMSTATE_INT32(cq_pending, NvmeCtrl),
+
+        VMSTATE_UINT64(host_timestamp, NvmeCtrl),
+        VMSTATE_UINT64(timestamp_set_qemu_clock_ms, NvmeCtrl),
+        VMSTATE_UINT64(starttime_ms, NvmeCtrl),
+        VMSTATE_UINT16(temperature, NvmeCtrl),
+        VMSTATE_UINT8(smart_critical_warning, NvmeCtrl),
+
+        VMSTATE_UINT32(conf_msix_qsize, NvmeCtrl),
+        VMSTATE_UINT32(conf_ioqpairs, NvmeCtrl),
+        VMSTATE_UINT64(dbbuf_dbs, NvmeCtrl),
+        VMSTATE_UINT64(dbbuf_eis, NvmeCtrl),
+        VMSTATE_BOOL(dbbuf_enabled, NvmeCtrl),
+
+        VMSTATE_UINT8(aer_mask, NvmeCtrl),
+        VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC(
+            aer_reqs, NvmeCtrl, outstanding_aers, 0, nvme_vmstate_request, NvmeRequest),
+        VMSTATE_QTAILQ_V(aer_queue, NvmeCtrl, 1, nvme_vmstate_async_event,
+                         NvmeAsyncEvent, entry),
+        VMSTATE_INT32(aer_queued, NvmeCtrl),
+
+        VMSTATE_END_OF_LIST()
+    },
 };
 
 static void nvme_class_init(ObjectClass *oc, const void *data)
diff --git a/hw/nvme/nvme.h b/hw/nvme/nvme.h
index 457b6637249..9c5f53c688c 100644
--- a/hw/nvme/nvme.h
+++ b/hw/nvme/nvme.h
@@ -638,6 +638,7 @@ typedef struct NvmeCtrl {
 
     NvmeNamespace   namespace;
     NvmeNamespace   *namespaces[NVME_MAX_NAMESPACES + 1];
+    uint32_t        num_queues;
     NvmeSQueue      **sq;
     NvmeCQueue      **cq;
     NvmeSQueue      admin_sq;
@@ -669,6 +670,7 @@ typedef struct NvmeCtrl {
 
     /* Migration-related stuff */
     Error *migration_blocker;
+    bool stop_processing_sq;
 } NvmeCtrl;
 
 typedef enum NvmeResetType {
diff --git a/hw/nvme/trace-events b/hw/nvme/trace-events
index 6be0bfa1c1f..8e5544e0008 100644
--- a/hw/nvme/trace-events
+++ b/hw/nvme/trace-events
@@ -7,6 +7,17 @@ pci_nvme_dbbuf_config(uint64_t dbs_addr, uint64_t eis_addr) "dbs_addr=0x%"PRIx64
 pci_nvme_map_addr(uint64_t addr, uint64_t len) "addr 0x%"PRIx64" len %"PRIu64""
 pci_nvme_map_addr_cmb(uint64_t addr, uint64_t len) "addr 0x%"PRIx64" len %"PRIu64""
 pci_nvme_map_prp(uint64_t trans_len, uint32_t len, uint64_t prp1, uint64_t prp2, int num_prps) "trans_len %"PRIu64" len %"PRIu32" prp1 0x%"PRIx64" prp2 0x%"PRIx64" num_prps %d"
+pci_nvme_pre_save_enter(void *n) "n=%p"
+pci_nvme_pre_save_ns_drain(void *n, int i) "n=%p i=%d"
+pci_nvme_pre_save_sq_out_req_drain_wait(void *n, int i, uint32_t head, uint32_t tail, uint32_t size) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32" size=0x%"PRIx32""
+pci_nvme_pre_save_sq_out_req_drain_wait_end(void *n, int i, uint32_t head, uint32_t tail) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32""
+pci_nvme_pre_save_cq_req_drain_wait(void *n, int i, uint32_t head, uint32_t tail, uint32_t size) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32" size=0x%"PRIx32""
+pci_nvme_pre_save_cq_req_drain_wait_end(void *n, int i, uint32_t head, uint32_t tail) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32""
+pci_nvme_pre_save_aer(uint8_t typ, uint8_t info, uint8_t log_page) "type 0x%"PRIx8" info 0x%"PRIx8" lid 0x%"PRIx8""
+pci_nvme_post_load_enter(void *n) "n=%p"
+pci_nvme_post_load_restore_cq(void *n, int i, uint32_t head, uint32_t tail, uint32_t size) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32" size=0x%"PRIx32""
+pci_nvme_post_load_restore_sq(void *n, int i, uint32_t head, uint32_t tail, uint32_t size) "n=%p i=%d head=0x%"PRIx32" tail=0x%"PRIx32" size=0x%"PRIx32""
+pci_nvme_post_load_aer(uint8_t typ, uint8_t info, uint8_t log_page) "type 0x%"PRIx8" info 0x%"PRIx8" lid 0x%"PRIx8""
 pci_nvme_map_sgl(uint8_t typ, uint64_t len) "type 0x%"PRIx8" len %"PRIu64""
 pci_nvme_io_cmd(uint16_t cid, uint32_t nsid, uint16_t sqid, uint8_t opcode, const char *opname) "cid %"PRIu16" nsid 0x%"PRIx32" sqid %"PRIu16" opc 0x%"PRIx8" opname '%s'"
 pci_nvme_admin_cmd(uint16_t cid, uint16_t sqid, uint8_t opcode, const char *opname) "cid %"PRIu16" sqid %"PRIu16" opc 0x%"PRIx8" opname '%s'"
-- 
2.47.3

[PATCH v3 6/6] tests/functional/x86_64: add migration test for NVMe device

[Alexander Mikhalitsyn]

From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

Introduce a very simple test to ensure that NVMe device
migration works fine.

Test plan is simple:
1. prepare VM with NVMe device
2. run workload that produces relatively heavy IO on the device
3. migrate VM
4. ensure that workload is alive and finishes without errors

Test can be run as simple as:
$ meson test 'func-x86_64-nvme_migration' --setup thorough -C build

In the future we can extend this approach, and introduce some
fio-based tests. And probably, it makes sense to make this test
to apply not only to NVMe device, but also virtio-{blk,scsi},
ide, sata and other migratable devices.

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
---
 tests/functional/x86_64/meson.build           |   1 +
 .../functional/x86_64/test_nvme_migration.py  | 159 ++++++++++++++++++
 2 files changed, 160 insertions(+)
 create mode 100755 tests/functional/x86_64/test_nvme_migration.py

diff --git a/tests/functional/x86_64/meson.build b/tests/functional/x86_64/meson.build
index 05e4914c772..a3b010d24c6 100644
--- a/tests/functional/x86_64/meson.build
+++ b/tests/functional/x86_64/meson.build
@@ -30,6 +30,7 @@ tests_x86_64_system_thorough = [
   'linux_initrd',
   'multiprocess',
   'netdev_ethtool',
+  'nvme_migration',
   'replay',
   'reverse_debug',
   'tuxrun',
diff --git a/tests/functional/x86_64/test_nvme_migration.py b/tests/functional/x86_64/test_nvme_migration.py
new file mode 100755
index 00000000000..3788a8e3473
--- /dev/null
+++ b/tests/functional/x86_64/test_nvme_migration.py
@@ -0,0 +1,159 @@
+#!/usr/bin/env python3
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# x86_64 NVMe migration test
+
+from migration import MigrationTest
+from qemu_test import QemuSystemTest, Asset
+from qemu_test import wait_for_console_pattern
+from qemu_test import exec_command, exec_command_and_wait_for_pattern
+
+
+class X8664NVMeMigrationTest(MigrationTest):
+    ASSET_KERNEL = Asset(
+        ('https://archives.fedoraproject.org/pub/archive/fedora/linux/releases'
+         '/31/Server/x86_64/os/images/pxeboot/vmlinuz'),
+        'd4738d03dbbe083ca610d0821d0a8f1488bebbdccef54ce33e3adb35fda00129')
+
+    ASSET_INITRD = Asset(
+        ('https://archives.fedoraproject.org/pub/archive/fedora/linux/releases'
+         '/31/Server/x86_64/os/images/pxeboot/initrd.img'),
+        '277cd6c7adf77c7e63d73bbb2cded8ef9e2d3a2f100000e92ff1f8396513cd8b')
+
+    ASSET_DISKIMAGE = Asset(
+        ('https://archives.fedoraproject.org/pub/archive/fedora/linux/releases'
+         '/31/Cloud/x86_64/images/Fedora-Cloud-Base-31-1.9.x86_64.qcow2'),
+        'e3c1b309d9203604922d6e255c2c5d098a309c2d46215d8fc026954f3c5c27a0')
+
+    DEFAULT_KERNEL_PARAMS = ('root=/dev/nvme0n1p1 console=ttyS0 net.ifnames=0 '
+                             'rd.rescue quiet')
+
+    def wait_for_console_pattern(self, success_message, vm):
+        wait_for_console_pattern(
+            self,
+            success_message,
+            failure_message="Kernel panic - not syncing",
+            vm=vm,
+        )
+
+    def exec_command_and_check(self, command, vm):
+        prompt = '# '
+        exec_command_and_wait_for_pattern(self,
+                                        f"{command} && echo OK || echo FAIL",
+                                        'FAIL', vm=vm)
+        # Note, that commands we send to the console are echo-ed back, so if we have a word "FAIL"
+        # in the command itself, we should expect to see it once.
+        wait_for_console_pattern(self, 'OK', failure_message="FAIL", vm=vm)
+        self.wait_for_console_pattern(prompt, vm)
+
+    def configure_machine(self, vm):
+        kernel_path = self.ASSET_KERNEL.fetch()
+        initrd_path = self.ASSET_INITRD.fetch()
+        diskimage_path = self.ASSET_DISKIMAGE.fetch()
+
+        vm.set_console()
+        vm.add_args("-cpu", "max")
+        vm.add_args("-m", "2G")
+        vm.add_args("-accel", "kvm")
+
+        vm.add_args('-drive',
+                         f'file={diskimage_path},if=none,id=drv0,snapshot=on')
+        vm.add_args('-device', 'nvme,bus=pcie.0,' +
+                         'drive=drv0,id=nvme-disk0,serial=nvmemigratetest,bootindex=1')
+
+        vm.add_args(
+            "-kernel",
+            kernel_path,
+            "-initrd",
+            initrd_path,
+            "-append",
+            self.DEFAULT_KERNEL_PARAMS
+        )
+
+    def launch_source_vm(self, vm):
+        vm.launch()
+
+        self.wait_for_console_pattern('Entering emergency mode.', vm)
+        prompt = '# '
+        self.wait_for_console_pattern(prompt, vm)
+
+        # Synchronize on NVMe driver creating the root device
+        exec_command_and_wait_for_pattern(self,
+                        "while ! (dmesg -c | grep nvme0n1:) ; do sleep 1 ; done",
+                        "nvme0n1", vm=vm)
+        self.wait_for_console_pattern(prompt, vm)
+
+        # prepare system
+        exec_command_and_wait_for_pattern(self, 'mount /dev/nvme0n1p1 /sysroot',
+                                          prompt, vm=vm)
+        exec_command_and_wait_for_pattern(self, 'chroot /sysroot',
+                                          prompt, vm=vm)
+        exec_command_and_wait_for_pattern(self, 'mount -t proc proc /proc',
+                                          prompt, vm=vm)
+        exec_command_and_wait_for_pattern(self, 'mount -t sysfs sysfs /sys',
+                                          prompt, vm=vm)
+
+        # Run workload before migration to check if it continues to run properly after migration
+        #
+        # Workload is simple: it continuously calculates checksums of all files in /usr/bin
+        # to generate some I/O load on the NVMe disk and at the same time it drops caches to
+        # make sure that we have some read I/O on the disk as well.
+        # If there are any issues with the migration of the NVMe device, we should see errors
+        # in dmesg and consequently in the workload log.
+        exec_command_and_wait_for_pattern(self,
+                                        "(while [ ! -f /tmp/test_nvme_migration_workload.stop ]; do \
+                                            rm -f /tmp/test_nvme_migration_workload.iteration_finished; \
+                                            echo 3 > /proc/sys/vm/drop_caches; \
+                                            find /usr/bin -type f -exec cksum {} \\;; \
+                                            touch /tmp/test_nvme_migration_workload.iteration_finished; \
+                                        done) > /dev/null 2> /tmp/test_nvme_migration_workload.errors &",
+                                        prompt, vm=vm)
+        exec_command_and_wait_for_pattern(self, 'echo $! > /tmp/test_nvme_migration_workload.pid',
+                                          prompt, vm=vm)
+
+        # check if process is alive and running
+        self.exec_command_and_check("kill -0 $(cat /tmp/test_nvme_migration_workload.pid)", vm)
+
+    def assert_dest_vm(self, vm):
+        prompt = '# '
+
+        # check if process is alive and running after migration, if not - fail the test
+        self.exec_command_and_check("kill -0 $(cat /tmp/test_nvme_migration_workload.pid)", vm)
+
+        # signal workload to stop
+        exec_command_and_wait_for_pattern(self, 'touch /tmp/test_nvme_migration_workload.stop',
+                                          prompt, vm=vm)
+
+        # wait workload to finish, because we want to examine log to see if there are any errors
+        exec_command_and_wait_for_pattern(self,
+                                        "while [ ! -f /tmp/test_nvme_migration_workload.iteration_finished ]; do sleep 1; done;",
+                                        prompt, vm=vm)
+
+        exec_command_and_wait_for_pattern(self, 'cat /tmp/test_nvme_migration_workload.errors',
+                                          prompt, vm=vm)
+
+        # fail the test if non-empty
+        self.exec_command_and_check("[ ! -s /tmp/test_nvme_migration_workload.errors ]", vm)
+
+    def test_migration_with_tcp_localhost(self):
+        self.set_machine('q35')
+        self.require_accelerator("kvm")
+
+        self.migration_with_tcp_localhost()
+
+    def test_migration_with_unix(self):
+        self.set_machine('q35')
+        self.require_accelerator("kvm")
+
+        self.migration_with_unix()
+
+    def test_migration_with_exec(self):
+        self.set_machine('q35')
+        self.require_accelerator("kvm")
+
+        self.migration_with_exec()
+
+
+if __name__ == '__main__':
+    MigrationTest.main()
-- 
2.47.3

Re: [PATCH v3 1/6] migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC

[Peter Xu]

On Fri, Mar 06, 2026 at 04:03:37PM +0100, Alexander Mikhalitsyn wrote:
> +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
> +    .name       = (stringify(_field)),                                \
> +    .version_id = (_version),                                         \
> +    .num_offset = vmstate_offset_value(_state, _field_num, uint8_t), \
> +    .info       = &vmstate_info_ptrs_array_entry,                     \
> +    .vmsd       = &(_vmsd),                                           \
> +    .start      = sizeof(_type),                                      \
> +    .size       = sizeof(_type *),                                    \
> +    .flags      = VMS_VARRAY_UINT8|VMS_POINTER,                      \
> +    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
> +}
> +
> +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
> +    .name       = (stringify(_field)),                                \
> +    .version_id = (_version),                                         \
> +    .num_offset = vmstate_offset_value(_state, _field_num, uint32_t), \
> +    .info       = &vmstate_info_ptrs_array_entry,                     \
> +    .vmsd       = &(_vmsd),                                           \
> +    .start      = sizeof(_type),                                      \
> +    .size       = sizeof(_type *),                                    \
> +    .flags      = VMS_VARRAY_UINT32|VMS_POINTER,                      \
> +    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
> +}

Hi, Alex,

Per previous discussion, I thought we plan to add a new VMS_* flag, am I
right?

https://lore.kernel.org/r/CAJqdLrrKK-pTzk+Qm_45p9A6DRgj4VbFzSb6vFtJTkpN3UaFpg@mail.gmail.com

-- 
Peter Xu

Re: [PATCH v3 1/6] migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC

[Alexander Mikhalitsyn]

Am Fr., 6. März 2026 um 16:55 Uhr schrieb Peter Xu <peterx@redhat.com>:
>
> On Fri, Mar 06, 2026 at 04:03:37PM +0100, Alexander Mikhalitsyn wrote:
> > +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
> > +    .name       = (stringify(_field)),                                \
> > +    .version_id = (_version),                                         \
> > +    .num_offset = vmstate_offset_value(_state, _field_num, uint8_t), \
> > +    .info       = &vmstate_info_ptrs_array_entry,                     \
> > +    .vmsd       = &(_vmsd),                                           \
> > +    .start      = sizeof(_type),                                      \
> > +    .size       = sizeof(_type *),                                    \
> > +    .flags      = VMS_VARRAY_UINT8|VMS_POINTER,                      \
> > +    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
> > +}
> > +
> > +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \
> > +    .name       = (stringify(_field)),                                \
> > +    .version_id = (_version),                                         \
> > +    .num_offset = vmstate_offset_value(_state, _field_num, uint32_t), \
> > +    .info       = &vmstate_info_ptrs_array_entry,                     \
> > +    .vmsd       = &(_vmsd),                                           \
> > +    .start      = sizeof(_type),                                      \
> > +    .size       = sizeof(_type *),                                    \
> > +    .flags      = VMS_VARRAY_UINT32|VMS_POINTER,                      \
> > +    .offset     = vmstate_offset_pointer(_state, _field, _type *),    \
> > +}
>
> Hi, Alex,

Hi Peter,

>
> Per previous discussion, I thought we plan to add a new VMS_* flag, am I
> right?

yes, yes, I'll do this in -v4, sorry for this. I was busy adding a
test for NVMe migration
and decided to send -v3 with this new test.

Sorry about confusing you.

Kind regards,
Alex

>
> https://lore.kernel.org/r/CAJqdLrrKK-pTzk+Qm_45p9A6DRgj4VbFzSb6vFtJTkpN3UaFpg@mail.gmail.com
>
> --
> Peter Xu
>

Re: [PATCH v3 1/6] migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC

[Peter Xu]

On Fri, Mar 06, 2026 at 04:57:56PM +0100, Alexander Mikhalitsyn wrote:
> yes, yes, I'll do this in -v4, sorry for this. I was busy adding a
> test for NVMe migration
> and decided to send -v3 with this new test.
> 
> Sorry about confusing you.

Ahhh, no worries.  Just to say, if you send a patchset without RFC or any
mark, it by default says: "please consider merging it".

Good to know we're still on the same page.

-- 
Peter Xu

Re: [PATCH v3 1/6] migration: add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC

[Alexander Mikhalitsyn]

Am Fr., 6. März 2026 um 17:34 Uhr schrieb Peter Xu <peterx@redhat.com>:
>
> On Fri, Mar 06, 2026 at 04:57:56PM +0100, Alexander Mikhalitsyn wrote:
> > yes, yes, I'll do this in -v4, sorry for this. I was busy adding a
> > test for NVMe migration
> > and decided to send -v3 with this new test.
> >
> > Sorry about confusing you.

Hi Peter,

>
> Ahhh, no worries.  Just to say, if you send a patchset without RFC or any
> mark, it by default says: "please consider merging it".

yeah, sorry about this again.

>
> Good to know we're still on the same page.

yep, I've just sent a version 4 and it is based on your idea with new
VMS_ARRAY_OF_POINTER_ALLOW_NULL flag. Hope that I get everything right.
Also, it includes tests and many new asserts here and there :)

Kind regards,
Alex

>
> --
> Peter Xu
>