Re: [PATCH QEMU v25 12/17] vfio: Add function to start and stop dirty pages tracking

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

* Cornelia Huck (cohuck@redhat.com) wrote:
> On Sun, 21 Jun 2020 01:51:21 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
> > Call VFIO_IOMMU_DIRTY_PAGES ioctl to start and stop dirty pages tracking
> > for VFIO devices.
> > 
> > Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  hw/vfio/migration.c | 36 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 36 insertions(+)
> > 
> > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > index faacea5327cb..e0fbb3a01855 100644
> > --- a/hw/vfio/migration.c
> > +++ b/hw/vfio/migration.c
> > @@ -11,6 +11,7 @@
> >  #include "qemu/main-loop.h"
> >  #include "qemu/cutils.h"
> >  #include <linux/vfio.h>
> > +#include <sys/ioctl.h>
> >  
> >  #include "sysemu/runstate.h"
> >  #include "hw/vfio/vfio-common.h"
> > @@ -329,6 +330,32 @@ static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
> >      return qemu_file_get_error(f);
> >  }
> >  
> > +static int vfio_start_dirty_page_tracking(VFIODevice *vbasedev, bool start)
> 
> I find 'start' functions that may also stop something a bit confusing.
> Maybe vfio_toggle_dirty_page_tracking()?

I don't think toggle is any better; I always think of toggle as flipping
the state to the other state.
vfio_set_dirty_page_tracking maybe?

Dave


> > +{
> > +    int ret;
> > +    VFIOContainer *container = vbasedev->group->container;
> > +    struct vfio_iommu_type1_dirty_bitmap dirty = {
> > +        .argsz = sizeof(dirty),
> > +    };
> > +
> > +    if (start) {
> > +        if (vbasedev->device_state & VFIO_DEVICE_STATE_SAVING) {
> > +            dirty.flags = VFIO_IOMMU_DIRTY_PAGES_FLAG_START;
> > +        } else {
> > +            return -EINVAL;
> > +        }
> > +    } else {
> > +            dirty.flags = VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP;
> > +    }
> > +
> > +    ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, &dirty);
> > +    if (ret) {
> > +        error_report("Failed to set dirty tracking flag 0x%x errno: %d",
> > +                     dirty.flags, errno);
> > +    }
> > +    return ret;
> > +}
> > +
> >  /* ---------------------------------------------------------------------- */
> >  
> >  static int vfio_save_setup(QEMUFile *f, void *opaque)
> > @@ -360,6 +387,11 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
> >          return ret;
> >      }
> >  
> > +    ret = vfio_start_dirty_page_tracking(vbasedev, true);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
> >      qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> >  
> >      ret = qemu_file_get_error(f);
> > @@ -375,6 +407,8 @@ static void vfio_save_cleanup(void *opaque)
> >      VFIODevice *vbasedev = opaque;
> >      VFIOMigration *migration = vbasedev->migration;
> >  
> > +    vfio_start_dirty_page_tracking(vbasedev, false);
> 
> I suppose we can't do anything useful if stopping dirty page tracking
> fails?
> 
> > +
> >      if (migration->region.mmaps) {
> >          vfio_region_unmap(&migration->region);
> >      }
> > @@ -706,6 +740,8 @@ static void vfio_migration_state_notifier(Notifier *notifier, void *data)
> >          if (ret) {
> >              error_report("%s: Failed to set state RUNNING", vbasedev->name);
> >          }
> > +
> > +        vfio_start_dirty_page_tracking(vbasedev, false);
> >      }
> >  }
> >  
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK