[PATCH v4] failover: unregister ROM on unplug

[Laurent Vivier]

The intend of failover is to allow to migrate a VM with a VFIO
networking card without disrupting the network operation by switching
to a virtio-net device during the migration.

This simple change allows to test failover with a simulated device
like e1000e rather than a vfio device, even if it's useless in real
life it can help to debug failover.

This is interesting to developers that want to test failover on
a system with no vfio device. Moreover it simplifies host networking
configuration as we can use the same bridge for virtio-net and
the other failover networking device.

Without this change the migration of a system configured with failover
fails with:

  ...
  -device virtio-net-pci,id=virtionet0,failover=on,...  \
  -device e1000,failover_pair_id=virtionet0,... \
  ...

  (qemu) migrate ...

  Unknown ramblock "0000:00:01.1:00.0/e1000e.rom", cannot accept migration
  error while loading state for instance 0x0 of device 'ram'
  load of migration failed: Invalid argument

This happens because QEMU correctly unregisters the interface vmstate but
not the ROM one. This patch fixes that.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---

Notes:
    v4:
      export and use pci_del_option_rom()
    
    v3:
      remove useless space before comma
    
    v2:
      reset has_rom to false
      update commit log message

 include/hw/pci/pci.h | 2 ++
 hw/net/virtio-net.c  | 1 +
 hw/pci/pci.c         | 3 +--
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index d0f4266e3725..84707034cbf8 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -369,6 +369,8 @@ void pci_register_vga(PCIDevice *pci_dev, MemoryRegion *mem,
 void pci_unregister_vga(PCIDevice *pci_dev);
 pcibus_t pci_get_bar_addr(PCIDevice *pci_dev, int region_num);
 
+void pci_del_option_rom(PCIDevice *pdev);
+
 int pci_add_capability(PCIDevice *pdev, uint8_t cap_id,
                        uint8_t offset, uint8_t size,
                        Error **errp);
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 16d20cdee52a..d6f03633f1b3 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3256,6 +3256,7 @@ static void virtio_net_handle_migration_primary(VirtIONet 
*n, MigrationState *s)
     if (migration_in_setup(s) && !should_be_hidden) {
         if (failover_unplug_primary(n, dev)) {
             vmstate_unregister(VMSTATE_IF(dev), qdev_get_vmsd(dev), dev);
+            pci_del_option_rom(PCI_DEVICE(dev));
             qapi_event_send_unplug_primary(dev->id);
             qatomic_set(&n->failover_primary_hidden, true);
         } else {
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 23d2ae2ab232..c210d92b5ba7 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -228,7 +228,6 @@ static PCIBus *pci_find_bus_nr(PCIBus *bus, int bus_num);
 static void pci_update_mappings(PCIDevice *d);
 static void pci_irq_handler(void *opaque, int irq_num, int level);
 static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom, Error **);
-static void pci_del_option_rom(PCIDevice *pdev);
 
 static uint16_t pci_default_sub_vendor_id = PCI_SUBVENDOR_ID_REDHAT_QUMRANET;
 static uint16_t pci_default_sub_device_id = PCI_SUBDEVICE_ID_QEMU;
@@ -2429,7 +2428,7 @@ static void pci_add_option_rom(PCIDevice *pdev, bool 
is_default_rom,
     pci_register_bar(pdev, PCI_ROM_SLOT, 0, &pdev->rom);
 }
 
-static void pci_del_option_rom(PCIDevice *pdev)
+void pci_del_option_rom(PCIDevice *pdev)
 {
     if (!pdev->has_rom)
         return;
-- 
2.31.1