[Qemu-arm] [RFC v4 3/3] hw/intc/arm_gicv3_its: Allow save/restore

[Eric Auger <eric.auger@redhat.com>]

We change the restoration priority of both the GICv3 and ITS. The
GICv3 must be restored before the ITS and the ITS needs to be restored
before PCIe devices since it translates their MSI transactions.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---
v2 -> v3:
- reword migration blocker message
- remove unmigratable setting to false

v1 -> v2:
- handle case where migrate_add_blocker fails
- add comments along with ITS and GICv3 migration priorities
---
 hw/intc/arm_gicv3_common.c     |  1 +
 hw/intc/arm_gicv3_its_common.c |  2 +-
 hw/intc/arm_gicv3_its_kvm.c    | 24 ++++++++++++------------
 include/migration/vmstate.h    |  2 ++
 4 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
index c6493d6..4228b7c 100644
--- a/hw/intc/arm_gicv3_common.c
+++ b/hw/intc/arm_gicv3_common.c
@@ -145,6 +145,7 @@ static const VMStateDescription vmstate_gicv3 = {
     .minimum_version_id = 1,
     .pre_save = gicv3_pre_save,
     .post_load = gicv3_post_load,
+    .priority = MIG_PRI_GICV3,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(gicd_ctlr, GICv3State),
         VMSTATE_UINT32_ARRAY(gicd_statusr, GICv3State, 2),
diff --git a/hw/intc/arm_gicv3_its_common.c b/hw/intc/arm_gicv3_its_common.c
index efab8c7..22ce4c4 100644
--- a/hw/intc/arm_gicv3_its_common.c
+++ b/hw/intc/arm_gicv3_its_common.c
@@ -48,7 +48,7 @@ static const VMStateDescription vmstate_its = {
     .name = "arm_gicv3_its",
     .pre_save = gicv3_its_pre_save,
     .post_load = gicv3_its_post_load,
-    .unmigratable = true,
+    .priority = MIG_PRI_GICV3_ITS,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(ctlr, GICv3ITSState),
         VMSTATE_UINT32(iidr, GICv3ITSState),
diff --git a/hw/intc/arm_gicv3_its_kvm.c b/hw/intc/arm_gicv3_its_kvm.c
index bc4722b..9787c4c 100644
--- a/hw/intc/arm_gicv3_its_kvm.c
+++ b/hw/intc/arm_gicv3_its_kvm.c
@@ -76,18 +76,6 @@ static void kvm_arm_its_realize(DeviceState *dev, Error **errp)
     GICv3ITSState *s = ARM_GICV3_ITS_COMMON(dev);
     Error *local_err = NULL;
 
-    /*
-     * Block migration of a KVM GICv3 ITS device: the API for saving and
-     * restoring the state in the kernel is not yet available
-     */
-    error_setg(&s->migration_blocker, "vITS migration is not implemented");
-    migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        error_free(s->migration_blocker);
-        return;
-    }
-
     s->dev_fd = kvm_create_device(kvm_state, KVM_DEV_TYPE_ARM_VGIC_ITS, false);
     if (s->dev_fd < 0) {
         error_setg_errno(errp, -s->dev_fd, "error creating in-kernel ITS");
@@ -104,6 +92,18 @@ static void kvm_arm_its_realize(DeviceState *dev, Error **errp)
 
     gicv3_its_init_mmio(s, NULL);
 
+    if (!kvm_device_check_attr(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_ITS_REGS,
+        GITS_CTLR)) {
+        error_setg(&s->migration_blocker, "This operating system kernel "
+                   "does not support vGICv3 migration");
+        migrate_add_blocker(s->migration_blocker, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            error_free(s->migration_blocker);
+            return;
+        }
+    }
+
     kvm_msi_use_devid = true;
     kvm_gsi_direct_mapping = false;
     kvm_msi_via_irqfd_allowed = kvm_irqfds_enabled();
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index f2dbf84..8dab9c7 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -198,6 +198,8 @@ enum VMStateFlags {
 typedef enum {
     MIG_PRI_DEFAULT = 0,
     MIG_PRI_IOMMU,              /* Must happen before PCI devices */
+    MIG_PRI_GICV3_ITS,          /* Must happen before PCI devices */
+    MIG_PRI_GICV3,              /* Must happen before the ITS */
     MIG_PRI_MAX,
 } MigrationPriority;
 
-- 
2.5.5