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

[Jens Freimann]

On Mon, Oct 21, 2019 at 03:45:04PM +0200, Cornelia Huck wrote:
> On Fri, 18 Oct 2019 22:20:40 +0200
> Jens Freimann <address@hidden> 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 <address@hidden>
> > ---
> >  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.

You're right.

> > +        }
> > +    } 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.

Yes, so I moved it to this place now. This saves me cleanup up the
migration blocker in the above two cases. I don't jump to error if
adding the migration blocker failed, I just have to free the blocker
Error and can return.
> > @@ -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?

yes, added the same check here.

Thanks Conny!

regards,
Jens