Re: [PATCH QEMU v22 08/18] vfio: Register SaveVMHandlers for VFIO device

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

* Kirti Wankhede (kwankhede@nvidia.com) 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 <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  hw/vfio/migration.c  | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/trace-events |  2 ++
>  2 files changed, 75 insertions(+)
> 
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index c2f5564b51c3..773c8d16b1c1 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -8,12 +8,14 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu/main-loop.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"
> @@ -24,6 +26,17 @@
>  #include "pci.h"
>  #include "trace.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;
> @@ -126,6 +139,64 @@ 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.index,
> +                         strerror(-ret));
> +            return ret;
> +        }
> +    }
> +
> +    ret = vfio_migration_set_state(vbasedev, ~0, 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;
> @@ -192,6 +263,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>          return ret;
>      }
>  
> +    register_savevm_live("vfio", VMSTATE_INSTANCE_ID_ANY, 1,
> +                         &savevm_vfio_handlers, vbasedev);

I see you changed the -1 to VMSTATE_INSTANCE_ID_ANY which is soemthing
I'd asked for in my review last month of v16.
But I also asked what happens with multiple devices and whether this was
working OK because I was worried about using the fixed name and multiple
instances of a register_savevm_live being rare.  Did you check that out?

Dave

>      vbasedev->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change,
>                                                            vbasedev);
>  
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index bd3d47b005cb..86c18def016e 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -149,3 +149,5 @@ 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)"
> -- 
> 2.7.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK