Re: [Qemu-devel] [RFC PATCH V4 1/4] vfio: introduce a new VFIO subregion for mdev device migration support

[Kirti Wankhede]

On 4/10/2018 11:32 AM, Yulei Zhang wrote:
> New VFIO sub region VFIO_REGION_SUBTYPE_DEVICE_STATE is added
> to fetch and restore the status of mdev device vGPU during the
> live migration.
> 
> Signed-off-by: Yulei Zhang <address@hidden>
> ---
>  hw/vfio/pci.c              | 25 ++++++++++++++++++++++++-
>  hw/vfio/pci.h              |  2 ++
>  linux-headers/linux/vfio.h |  9 ++++++---
>  3 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index c977ee3..f98a9dd 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -32,6 +32,7 @@
>  #include "pci.h"
>  #include "trace.h"
>  #include "qapi/error.h"
> +#include "migration/blocker.h"
>  
>  #define MSIX_CAP_LENGTH 12
>  
> @@ -2821,6 +2822,25 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>          vfio_vga_quirk_setup(vdev);
>      }
>  
> +    struct vfio_region_info *device_state;
> +    /* device state region setup */
> +    if (!vfio_get_dev_region_info(&vdev->vbasedev,
> +                VFIO_REGION_TYPE_PCI_VENDOR_TYPE,
> +                VFIO_REGION_SUBTYPE_DEVICE_STATE, &device_state)) {
> +        memcpy(&vdev->device_state, device_state,
> +               sizeof(struct vfio_region_info));
> +        g_free(device_state);
> +    } else {
> +        error_setg(&vdev->migration_blocker,
> +                "Migration disabled: cannot support device state region");
> +        migrate_add_blocker(vdev->migration_blocker, &err);
> +        if (err) {
> +            error_propagate(errp, err);
> +            error_free(vdev->migration_blocker);
> +            goto error;
> +        }
> +    }
> +

I think there should be a _PROBE ioctl before trying to setup region for
migration. If vfio device driver or vendor driver for mdev device
supports migration capability, _PROBE ioctl should return success along
with region's information <index, size> which can be used to setup the
region.


>      for (i = 0; i < PCI_ROM_SLOT; i++) {
>          vfio_bar_quirk_setup(vdev, i);
>      }
> @@ -2884,6 +2904,10 @@ out_teardown:
>      vfio_teardown_msi(vdev);
>      vfio_bars_exit(vdev);
>  error:
> +    if (vdev->migration_blocker) {
> +        migrate_del_blocker(vdev->migration_blocker);
> +        error_free(vdev->migration_blocker);
> +    }
>      error_prepend(errp, ERR_PREFIX, vdev->vbasedev.name);
>  }
>  
> @@ -3009,7 +3033,6 @@ static Property vfio_pci_dev_properties[] = {
>  
>  static const VMStateDescription vfio_pci_vmstate = {
>      .name = "vfio-pci",
> -    .unmigratable = 1,

Based on the result of above _PROBE ioctl, 'unmigratable' should be set
if vendor driver doesn't support migration capability.

Thanks,
Kirti

>  };
>  
>  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> index 502a575..0ee1724 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -116,6 +116,8 @@ typedef struct VFIOPCIDevice {
>      VFIOBAR bars[PCI_NUM_REGIONS - 1]; /* No ROM */
>      VFIOVGA *vga; /* 0xa0000, 0x3b0, 0x3c0 */
>      void *igd_opregion;
> +    struct vfio_region_info device_state;
> +    Error *migration_blocker;
>      PCIHostDeviceAddress host;
>      EventNotifier err_notifier;
>      EventNotifier req_notifier;
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 4312e96..e3380ad 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -297,9 +297,12 @@ struct vfio_region_info_cap_type {
>  #define VFIO_REGION_TYPE_PCI_VENDOR_MASK     (0xffff)
>  
>  /* 8086 Vendor sub-types */
> -#define VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION       (1)
> -#define VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG       (2)
> -#define VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG        (3)
> +#define VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION               (1)
> +#define VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG               (2)
> +#define VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG                (3)
> +
> +/* Mdev sub-type for device state save and restore */
> +#define VFIO_REGION_SUBTYPE_DEVICE_STATE     (4)
>  
>  /**
>   * VFIO_DEVICE_GET_IRQ_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 9,
>