Re: [PATCH v3] failover: unregister ROM on unplug

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Laurent Vivier (lvivier@redhat.com) 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>
> ---
> 
> Notes:
>     v3:
>       remove useless space before comma
>     
>     v2:
>       reset has_rom to false
>       update commit log message
> 
>  hw/net/virtio-net.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 16d20cdee52a..c0c2ec1ebb98 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -3256,6 +3256,10 @@ 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);
> +            if (PCI_DEVICE(dev)->has_rom) {
> +                PCI_DEVICE(dev)->has_rom = false;
> +                vmstate_unregister_ram(&PCI_DEVICE(dev)->rom, dev);
> +            }

Not actually originated by your fix, but....

Why doesn't failover_replug_primary re-add the vmstates?

(I did wonder if passing rom-file="" to the e1000 would help in your
testing case, but it still creates the RAM image).

Dave

>              qapi_event_send_unplug_primary(dev->id);
>              qatomic_set(&n->failover_primary_hidden, true);
>          } else {
> -- 
> 2.31.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK