Re: [Qemu-devel] [PATCH v4 07/13] vfio: Register SaveVMHandlers for VFIO device

[Dr. David Alan Gilbert]

* Kirti Wankhede (address@hidden) wrote:
> Define flags to be used as delimeter in migration file stream.
> 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 <address@hidden>
> Reviewed-by: Neo Jia <address@hidden>
> ---
>  hw/vfio/migration.c | 76 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 75 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 7f9858e6c995..fe0887c27664 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -22,6 +22,17 @@
>  #include "exec/ram_addr.h"
>  #include "pci.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 void vfio_migration_region_exit(VFIODevice *vbasedev)
>  {
>      VFIOMigration *migration = vbasedev->migration;
> @@ -96,6 +107,69 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, 
> uint32_t state)
>      return 0;
>  }
>  
> +/* ---------------------------------------------------------------------- */
> +
> +static int vfio_save_setup(QEMUFile *f, void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    VFIOMigration *migration = vbasedev->migration;
> +    int ret;
> +
> +    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);
> +
> +    if (migration->region.buffer.mmaps) {
> +        qemu_mutex_lock_iothread();
> +        ret = vfio_region_mmap(&migration->region.buffer);
> +        qemu_mutex_unlock_iothread();
> +        if (ret) {
> +            error_report("Failed to mmap VFIO migration region %d: %s",
> +                         migration->region.index, strerror(-ret));
> +            return ret;
> +        }
> +    }
> +
> +    if (vbasedev->vm_running) {
> +        ret = vfio_migration_set_state(vbasedev,
> +                         VFIO_DEVICE_STATE_RUNNING | 
> VFIO_DEVICE_STATE_SAVING);
> +        if (ret) {
> +            error_report("Failed to set state RUNNING and SAVING");
> +            return ret;
> +        }
> +    } else {
> +        ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_SAVING);
> +        if (ret) {
> +            error_report("Failed to set state STOP and SAVING");
> +            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.buffer.mmaps) {
> +        vfio_region_unmap(&migration->region.buffer);
> +    }
> +}
> +
> +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;
> @@ -169,7 +243,7 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>      }
>  
>      qemu_mutex_init(&vbasedev->migration->lock);
> -
> +    register_savevm_live(NULL, "vfio", -1, 1, &savevm_vfio_handlers, 
> vbasedev);

Does this work OK with multiple devices?
I think I'd expected you to pass a DeviceState as the first parameter
for a real device like vfio.
'ram' and 'block' don't need to because they iterate over all RAM
devices inside their save_setup's and similar handlers;  for vfio I'd
expect it to be per-device.

Dave

>      vbasedev->vm_state = 
> qemu_add_vm_change_state_handler(vfio_vmstate_change,
>                                                            vbasedev);
>  
> -- 
> 2.7.0
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK