Re: [Qemu-devel] [PATCH 3/9] vfio: unplug failover primary device before migration

[Jens Freimann]

On Mon, Aug 12, 2019 at 05:18:54PM +0200, Cornelia Huck wrote:
> On Fri,  2 Aug 2019 17:05:59 +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 | 24 +++++++++++++++++++++++-
> >  hw/vfio/pci.h |  1 +
> >  2 files changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index d6ae9bd4ac..398d26669b 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -35,6 +35,9 @@
> >  #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)
> > @@ -2693,6 +2696,12 @@ static void vfio_unregister_req_notifier(VFIOPCIDevice 
> > *vdev)
> >      vdev->req_enabled = false;
> >  }
> >
> > +static int has_standby_arg(void *opaque, const char *name,
> > +                           const char *value, Error **errp)
> > +{
> > +    return strcmp(name, "standby") == 0;
> > +}
> > +
> >  static void vfio_realize(PCIDevice *pdev, Error **errp)
> >  {
> >      VFIOPCIDevice *vdev = PCI_VFIO(pdev);
> > @@ -2706,6 +2715,19 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
> >      int i, ret;
> >      bool is_mdev;
> >
> > +    if (qemu_opt_foreach(pdev->qdev.opts, has_standby_arg,
> > +                         (void *) pdev->qdev.opts, &err) == 0) {
> > +        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);
> > +            error_free(vdev->migration_blocker);
> > +        }
> > +    } else {
> > +        pdev->qdev.allow_unplug_during_migration = true;
>
> I think you add this only in the next patch?

you're right, will fix
> > +    }
> > +
> >      if (!vdev->vbasedev.sysfsdev) {
> >          if (!(~vdev->host.domain || ~vdev->host.bus ||
> >                ~vdev->host.slot || ~vdev->host.function)) {
> > @@ -3148,7 +3170,7 @@ static Property vfio_pci_dev_properties[] = {
> >
> >  static const VMStateDescription vfio_pci_vmstate = {
> >      .name = "vfio-pci",
> > -    .unmigratable = 1,
> > +    .unmigratable = 0,
> >  };
> >
> >  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
> > diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> > index 27d58fc55b..0f6f8cb395 100644
> > --- a/hw/vfio/pci.h
> > +++ b/hw/vfio/pci.h
> > @@ -169,6 +169,7 @@ typedef struct VFIOPCIDevice {
> >      bool no_vfio_ioeventfd;
> >      bool enable_ramfb;
> >      VFIODisplay *dpy;
> > +    Error *migration_blocker;
> >  } VFIOPCIDevice;
> >
> >  uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
>
> This patch interacts with support for vfio migration (last posted in
> <address@hidden>, I've not seen
> a later version yet.)
>
> With that, we'd have three cases to consider:
> 1) device is a failover primary
> 2) device has a migration region
> 3) none of the above
>
> Can 1) and 2) happen simultaneously? If yes, what should take
> precedence?

See my reply to Alex. If I understand it right nothing needs to be
explicitly enabled for the migration region by the user. So if a user
explicitly sets the failover parameters for the devie I think it makes
sense that it should take precedence.

regards,
Jens