Re: [PATCH v4] failover: unregister ROM on unplug

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 21, 2021 at 06:09:05PM +0200, Laurent Vivier wrote:
> 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>


Build fails on qemu-system-m68k:

/usr/bin/ld: libqemu-m68k-softmmu.fa.p/hw_net_virtio-net.c.o: in function `virtio_net_handle_migration_primary':
/scm/qemu/build/../hw/net/virtio-net.c:3259: undefined reference to `pci_del_option_rom'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
make[1]: *** [Makefile:154: run-ninja] Error 1

It's not pretty to poke at pci from generic virtio.
Should we maybe wrap vmstate_unregister and pci_del_option_rom
to allow removing all migrateable things related to the device
in one go somehow?


> ---
> 
> 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