Re: [PATCH 11/11] vfio: unplug failover primary device before migration

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 18 Oct 2019 22:20:40 +0200
Jens Freimann <jfreimann@redhat.com> wrote:

> As usual block all vfio-pci devices from being migrated, but make an
> exception for failover primary devices. This is achieved by setting
> unmigratable to 0 but also add a migration blocker for all vfio-pci
> devices except failover primary devices. These will be unplugged before
> migration happens by the migration handler of the corresponding
> virtio-net standby device.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>  hw/vfio/pci.c | 31 +++++++++++++++++++++++++------
>  hw/vfio/pci.h |  1 +
>  2 files changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 12fac39804..a15b83c6b6 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -40,6 +40,9 @@
>  #include "pci.h"
>  #include "trace.h"
>  #include "qapi/error.h"
> +#include "migration/blocker.h"
> +#include "qemu/option.h"
> +#include "qemu/option_int.h"
>  
>  #define TYPE_VFIO_PCI "vfio-pci"
>  #define PCI_VFIO(obj)    OBJECT_CHECK(VFIOPCIDevice, obj, TYPE_VFIO_PCI)
> @@ -2712,12 +2715,26 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>      int i, ret;
>      bool is_mdev;
>  
> +    if (!pdev->net_failover_pair_id) {
> +        error_setg(&vdev->migration_blocker,
> +                "VFIO device doesn't support migration");
> +        ret = migrate_add_blocker(vdev->migration_blocker, &err);
> +        if (err) {
> +            error_propagate(errp, err);
> +            goto error;

This looks wrong, you haven't set up vbasedev.name yet.

> +        }
> +    } else {
> +            pdev->qdev.allow_unplug_during_migration = true;
> +    }
> +
>      if (!vdev->vbasedev.sysfsdev) {
>          if (!(~vdev->host.domain || ~vdev->host.bus ||
>                ~vdev->host.slot || ~vdev->host.function)) {
>              error_setg(errp, "No provided host device");
>              error_append_hint(errp, "Use -device vfio-pci,host=DDDD:BB:DD.F "
>                                "or -device vfio-pci,sysfsdev=PATH_TO_DEVICE\n");
> +            migrate_del_blocker(vdev->migration_blocker);
> +            error_free(vdev->migration_blocker);
>              return;
>          }
>          vdev->vbasedev.sysfsdev =
> @@ -2729,6 +2746,8 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>      if (stat(vdev->vbasedev.sysfsdev, &st) < 0) {
>          error_setg_errno(errp, errno, "no such host device");
>          error_prepend(errp, VFIO_MSG_PREFIX, vdev->vbasedev.sysfsdev);
> +        migrate_del_blocker(vdev->migration_blocker);
> +        error_free(vdev->migration_blocker);
>          return;
>      }

Might be a bit easier cleanup-wise if you set up the blocker resp.
allow unplug during migration only here. The only difference is that
you'll get a different error message when trying to set up a
non-failover device with invalid specs on a migratable-only setup.

>  
> @@ -3008,6 +3027,8 @@ out_teardown:
>      vfio_bars_exit(vdev);
>  error:
>      error_prepend(errp, VFIO_MSG_PREFIX, vdev->vbasedev.name);
> +    migrate_del_blocker(vdev->migration_blocker);
> +    error_free(vdev->migration_blocker);

Shouldn't you check whether migration_block has been set up, like in
the finalize routine?

>  }
>  
>  static void vfio_instance_finalize(Object *obj)
> @@ -3019,6 +3040,10 @@ static void vfio_instance_finalize(Object *obj)
>      vfio_bars_finalize(vdev);
>      g_free(vdev->emulated_config_bits);
>      g_free(vdev->rom);
> +    if (vdev->migration_blocker) {
> +        migrate_del_blocker(vdev->migration_blocker);
> +        error_free(vdev->migration_blocker);
> +    }
>      /*
>       * XXX Leaking igd_opregion is not an oversight, we can't remove the
>       * fw_cfg entry therefore leaking this allocation seems like the safest