Re: [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device

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

* Philippe Mathieu-Daudé (philmd@redhat.com) wrote:
> On 9/23/20 1:24 AM, Kirti Wankhede wrote:
> > Define flags to be used as delimeter in migration file stream.
> 
> Typo "delimiter".
> 
> > Added .save_setup and .save_cleanup functions. Mapped & unmapped migration
> > region from these functions at source during saving or pre-copy phase.
> > Set VFIO device state depending on VM's state. During live migration, VM is
> > running when .save_setup is called, _SAVING | _RUNNING state is set for VFIO
> > device. During save-restore, VM is paused, _SAVING state is set for VFIO device.
> > 
> > Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> > Reviewed-by: Neo Jia <cjia@nvidia.com>
> > ---
> >  hw/vfio/migration.c  | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  hw/vfio/trace-events |  2 ++
> >  2 files changed, 93 insertions(+)
> > 
> > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > index f650fe9fc3c8..8e8adaa25779 100644
> > --- a/hw/vfio/migration.c
> > +++ b/hw/vfio/migration.c
> > @@ -8,12 +8,15 @@
> >   */
> >  
> >  #include "qemu/osdep.h"
> > +#include "qemu/main-loop.h"
> > +#include "qemu/cutils.h"
> >  #include <linux/vfio.h>
> >  
> >  #include "sysemu/runstate.h"
> >  #include "hw/vfio/vfio-common.h"
> >  #include "cpu.h"
> >  #include "migration/migration.h"
> > +#include "migration/vmstate.h"
> >  #include "migration/qemu-file.h"
> >  #include "migration/register.h"
> >  #include "migration/blocker.h"
> > @@ -25,6 +28,17 @@
> >  #include "trace.h"
> >  #include "hw/hw.h"
> >  
> > +/*
> > + * Flags used as delimiter:
> > + * 0xffffffff => MSB 32-bit all 1s
> > + * 0xef10     => emulated (virtual) function IO
> > + * 0x0000     => 16-bits reserved for flags
> > + */
> > +#define VFIO_MIG_FLAG_END_OF_STATE      (0xffffffffef100001ULL)
> > +#define VFIO_MIG_FLAG_DEV_CONFIG_STATE  (0xffffffffef100002ULL)
> > +#define VFIO_MIG_FLAG_DEV_SETUP_STATE   (0xffffffffef100003ULL)
> > +#define VFIO_MIG_FLAG_DEV_DATA_STATE    (0xffffffffef100004ULL)
> > +
> >  static inline int vfio_mig_access(VFIODevice *vbasedev, void *val, int count,
> >                                    off_t off, bool iswrite)
> >  {
> > @@ -166,6 +180,65 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
> >      return 0;
> >  }
> >  
> > +/* ---------------------------------------------------------------------- */
> > +
> > +static int vfio_save_setup(QEMUFile *f, void *opaque)
> > +{
> > +    VFIODevice *vbasedev = opaque;
> > +    VFIOMigration *migration = vbasedev->migration;
> > +    int ret;
> > +
> > +    trace_vfio_save_setup(vbasedev->name);
> > +
> > +    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);
> > +
> > +    if (migration->region.mmaps) {
> > +        qemu_mutex_lock_iothread();
> > +        ret = vfio_region_mmap(&migration->region);
> > +        qemu_mutex_unlock_iothread();
> > +        if (ret) {
> > +            error_report("%s: Failed to mmap VFIO migration region %d: %s",
> > +                         vbasedev->name, migration->region.nr,
> > +                         strerror(-ret));
> > +            error_report("%s: Falling back to slow path", vbasedev->name);
> > +        }
> > +    }
> > +
> > +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_MASK,
> > +                                   VFIO_DEVICE_STATE_SAVING);
> > +    if (ret) {
> > +        error_report("%s: Failed to set state SAVING", vbasedev->name);
> > +        return ret;
> > +    }
> > +
> > +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> > +
> > +    ret = qemu_file_get_error(f);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static void vfio_save_cleanup(void *opaque)
> > +{
> > +    VFIODevice *vbasedev = opaque;
> > +    VFIOMigration *migration = vbasedev->migration;
> > +
> > +    if (migration->region.mmaps) {
> > +        vfio_region_unmap(&migration->region);
> > +    }
> > +    trace_vfio_save_cleanup(vbasedev->name);
> > +}
> > +
> > +static SaveVMHandlers savevm_vfio_handlers = {
> > +    .save_setup = vfio_save_setup,
> > +    .save_cleanup = vfio_save_cleanup,
> > +};
> > +
> > +/* ---------------------------------------------------------------------- */
> > +
> >  static void vfio_vmstate_change(void *opaque, int running, RunState state)
> >  {
> >      VFIODevice *vbasedev = opaque;
> > @@ -225,6 +298,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> >                                 struct vfio_region_info *info)
> >  {
> >      int ret = -EINVAL;
> > +    char id[256] = "";
> > +    Object *obj;
> >  
> >      if (!vbasedev->ops->vfio_get_object) {
> >          return ret;
> > @@ -241,6 +316,22 @@ static int vfio_migration_init(VFIODevice *vbasedev,
> >          return ret;
> >      }
> >  
> > +    obj = vbasedev->ops->vfio_get_object(vbasedev);
> > +
> > +    if (obj) {
> > +        DeviceState *dev = DEVICE(obj);
> > +        char *oid = vmstate_if_get_id(VMSTATE_IF(dev));
> > +
> > +        if (oid) {
> > +            pstrcpy(id, sizeof(id), oid);
> > +            pstrcat(id, sizeof(id), "/");
> > +            g_free(oid);
> > +        }
> > +    }
> > +    pstrcat(id, sizeof(id), "vfio");
> 
> Alternatively (easier to review, matter of taste):
> 
>  g_autofree char *path = NULL;
> 
>  if (oid) {
>    path = g_strdup_printf("%s/vfio",
>                           vmstate_if_get_id(VMSTATE_IF(obj)););
>  } else {
>    path = g_strdup("vfio");
>  }
>  strpadcpy(id, sizeof(id), path, '\0');

Maybe, although it's a straight copy of the magic in unregister_savevm.

Dave

> > +
> > +    register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, &savevm_vfio_handlers,
> > +                         vbasedev);
> >      vbasedev->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change,
> >                                                            vbasedev);
> >      vbasedev->migration_state.notify = vfio_migration_state_notifier;
> > diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> > index bcb3fa7314d7..982d8dccb219 100644
> > --- a/hw/vfio/trace-events
> > +++ b/hw/vfio/trace-events
> > @@ -152,3 +152,5 @@ vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d"
> >  vfio_migration_set_state(const char *name, uint32_t state) " (%s) state %d"
> >  vfio_vmstate_change(const char *name, int running, const char *reason, uint32_t dev_state) " (%s) running %d reason %s device state %d"
> >  vfio_migration_state_notifier(const char *name, const char *state) " (%s) state %s"
> > +vfio_save_setup(const char *name) " (%s)"
> > +vfio_save_cleanup(const char *name) " (%s)"
> > 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK