Re: [PATCH v16 QEMU 13/16] vfio: Add function to start and stop dirty pages tracking

[Kirti Wankhede]

On 4/2/2020 12:33 AM, Dr. David Alan Gilbert wrote:
> * Kirti Wankhede (address@hidden) wrote:
> > Call VFIO_IOMMU_DIRTY_PAGES ioctl to start and stop dirty pages tracking
> > for VFIO devices.
> >
> > Signed-off-by: Kirti Wankhede <address@hidden>
> > ---
> >   hw/vfio/migration.c | 36 ++++++++++++++++++++++++++++++++++++
> >   1 file changed, 36 insertions(+)
> >
> > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > index ab295d25620e..1827b7cfb316 100644
> > --- a/hw/vfio/migration.c
> > +++ b/hw/vfio/migration.c
> > @@ -9,6 +9,7 @@
> >   
> >   #include "qemu/osdep.h"
> >   #include "qemu/main-loop.h"
> > +#include <sys/ioctl.h>
> >   #include <linux/vfio.h>
> >   
> >   #include "sysemu/runstate.h"
> > @@ -296,6 +297,32 @@ 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)
> > +{
> > +    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 0;
> > +        }
> > +    } 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)
> > @@ -330,6 +357,11 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
> >        */
> >       qemu_put_be64(f, migration->region.size);
> >   
> > +    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);
> > @@ -346,6 +378,8 @@ static void vfio_save_cleanup(void *opaque)
> >       VFIODevice *vbasedev = opaque;
> >       VFIOMigration *migration = vbasedev->migration;
> >   
> > +    vfio_start_dirty_page_tracking(vbasedev, false);
>
> Shouldn't you check the return value?

Even if return value is checked, it will be ignored and this function 
returns void.

Thanks,
Kirti

> > +
> >       if (migration->region.mmaps) {
> >           vfio_region_unmap(&migration->region);
> >       }
> > @@ -669,6 +703,8 @@ 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);
> >       }
> >   }
> >   
> > --
> > 2.7.0
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK