Re: [PATCH v28 07/17] vfio: Register SaveVMHandlers for VFIO device

[Yan Zhao <yan.y.zhao@intel.com>]

On Fri, Oct 23, 2020 at 04:10:33PM +0530, Kirti Wankhede wrote:
> Define flags to be used as delimiter in migration stream for VFIO devices.
> Added .save_setup and .save_cleanup functions. Map & unmap 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  | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/trace-events |   2 +
>  2 files changed, 104 insertions(+)
> 
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index a0f0e79b9b73..94d2bdae5c54 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 +28,22 @@
>  #include "trace.h"
>  #include "hw/hw.h"
>  
> +/*
> + * Flags to be used as unique delimiters for VFIO devices in the migration
> + * stream. These flags are composed as:
> + * 0xffffffff => MSB 32-bit all 1s
> + * 0xef10     => Magic ID, represents emulated (virtual) function IO
> + * 0x0000     => 16-bits reserved for flags
> + *
> + * The beginning of state information is marked by _DEV_CONFIG_STATE,
> + * _DEV_SETUP_STATE, or _DEV_DATA_STATE, respectively. The end of a
> + * certain state information is marked by _END_OF_STATE.
> + */
> +#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)
>  {
> @@ -129,6 +148,75 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
>      return 0;
>  }
>  
> +static void vfio_migration_cleanup(VFIODevice *vbasedev)
> +{
> +    VFIOMigration *migration = vbasedev->migration;
> +
> +    if (migration->region.mmaps) {
> +        vfio_region_unmap(&migration->region);
> +    }
> +}
> +
> +/* ---------------------------------------------------------------------- */
> +
> +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) {
> +        /*
> +         * Calling vfio_region_mmap() from migration thread. Memory API called
> +         * from this function require locking the iothread when called from
> +         * outside the main loop thread.
> +         */
> +        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: %s",
> +                         vbasedev->name, 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;
> +    }
> +

is it possible to call vfio_update_pending() and vfio_save_buffer() here?
so that vendor driver has a chance to hook compatibility checking string
early in save_setup stage and can avoid to hook the string in both
precopy iteration stage and stop and copy stage.

But I think it's ok if we agree to add this later.

Besides that,
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>

> +    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;
> +
> +    vfio_migration_cleanup(vbasedev);
> +    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;
> @@ -217,6 +305,8 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>      int ret;
>      Object *obj;
>      VFIOMigration *migration;
> +    char id[256] = "";
> +    g_autofree char *path = NULL, *oid = NULL;
>  
>      if (!vbasedev->ops->vfio_get_object) {
>          return -EINVAL;
> @@ -247,6 +337,18 @@ static int vfio_migration_init(VFIODevice *vbasedev,
>      }
>  
>      migration->vbasedev = vbasedev;
> +
> +    oid = vmstate_if_get_id(VMSTATE_IF(DEVICE(obj)));
> +    if (oid) {
> +        path = g_strdup_printf("%s/vfio", oid);
> +    } else {
> +        path = g_strdup("vfio");
> +    }
> +    strpadcpy(id, sizeof(id), path, '\0');
> +
> +    register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, &savevm_vfio_handlers,
> +                         vbasedev);
> +
>      migration->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change,
>                                                             vbasedev);
>      migration->migration_state.notify = vfio_migration_state_notifier;
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index 78d7d83b5ef8..f148b5e828c1 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -151,3 +151,5 @@ 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
>