Re: [PATCH v2 8/8] vfio/migration: Allow live migration with vIOMMU without VFs using device dirty tracking

[Yi Liu <yi.l.liu@intel.com>]

On 2025/10/17 16:22, Zhenzhong Duan wrote:
> Commit e46883204c38 ("vfio/migration: Block migration with vIOMMU")
> introduces a migration blocker when vIOMMU is enabled, because we need
> to calculate the IOVA ranges for device dirty tracking. But this is
> unnecessary for iommu dirty tracking.
> 
> Limit the vfio_viommu_preset() check to those devices which use device
> dirty tracking. This allows live migration with VFIO devices which use
> iommu dirty tracking.
> 
> Introduce a helper vfio_device_dirty_pages_disabled() to facilicate it.

s/facilicate/facilitate/

Reviewed-by: Yi Liu <yi.l.liu@intel.com>

> 
> Suggested-by: Jason Zeng <jason.zeng@intel.com>
> Co-developed-by: Joao Martins <joao.m.martins@oracle.com>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Tested-by: Xudong Hao <xudong.hao@intel.com>
> Tested-by: Giovannio Cabiddu <giovanni.cabiddu@intel.com>
> ---
>   include/hw/vfio/vfio-device.h | 10 ++++++++++
>   hw/vfio/container.c           |  5 +----
>   hw/vfio/device.c              |  6 ++++++
>   hw/vfio/migration.c           |  6 +++---
>   4 files changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
> index 7e9aed6d3c..feda521514 100644
> --- a/include/hw/vfio/vfio-device.h
> +++ b/include/hw/vfio/vfio-device.h
> @@ -148,6 +148,16 @@ bool vfio_device_irq_set_signaling(VFIODevice *vbasedev, int index, int subindex
>   
>   void vfio_device_reset_handler(void *opaque);
>   bool vfio_device_is_mdev(VFIODevice *vbasedev);
> +/**
> + * vfio_device_dirty_pages_disabled: Check if device dirty tracking will be
> + * used for a VFIO device
> + *
> + * @vbasedev: The VFIODevice to transform
> + *
> + * Return: true if either @vbasedev doesn't support device dirty tracking or
> + * is forcedly disabled from command line, otherwise false.
> + */
> +bool vfio_device_dirty_pages_disabled(VFIODevice *vbasedev);
>   bool vfio_device_hiod_create_and_realize(VFIODevice *vbasedev,
>                                            const char *typename, Error **errp);
>   bool vfio_device_attach(char *name, VFIODevice *vbasedev,
> diff --git a/hw/vfio/container.c b/hw/vfio/container.c
> index 7706603c1c..8879da78c8 100644
> --- a/hw/vfio/container.c
> +++ b/hw/vfio/container.c
> @@ -178,10 +178,7 @@ bool vfio_container_devices_dirty_tracking_is_supported(
>       VFIODevice *vbasedev;
>   
>       QLIST_FOREACH(vbasedev, &bcontainer->device_list, container_next) {
> -        if (vbasedev->device_dirty_page_tracking == ON_OFF_AUTO_OFF) {
> -            return false;
> -        }
> -        if (!vbasedev->dirty_pages_supported) {
> +        if (vfio_device_dirty_pages_disabled(vbasedev)) {
>               return false;
>           }
>       }
> diff --git a/hw/vfio/device.c b/hw/vfio/device.c
> index 64f8750389..837872387f 100644
> --- a/hw/vfio/device.c
> +++ b/hw/vfio/device.c
> @@ -400,6 +400,12 @@ bool vfio_device_is_mdev(VFIODevice *vbasedev)
>       return subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
>   }
>   
> +bool vfio_device_dirty_pages_disabled(VFIODevice *vbasedev)
> +{
> +    return (!vbasedev->dirty_pages_supported ||
> +            vbasedev->device_dirty_page_tracking == ON_OFF_AUTO_OFF);
> +}
> +
>   bool vfio_device_hiod_create_and_realize(VFIODevice *vbasedev,
>                                            const char *typename, Error **errp)
>   {
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 1106ca7857..1093857a34 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -1213,8 +1213,7 @@ bool vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
>           return !vfio_block_migration(vbasedev, err, errp);
>       }
>   
> -    if ((!vbasedev->dirty_pages_supported ||
> -         vbasedev->device_dirty_page_tracking == ON_OFF_AUTO_OFF) &&
> +    if (vfio_device_dirty_pages_disabled(vbasedev) &&
>           !vbasedev->iommu_dirty_tracking) {
>           if (vbasedev->enable_migration == ON_OFF_AUTO_AUTO) {
>               error_setg(&err,
> @@ -1232,7 +1231,8 @@ bool vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
>           goto out_deinit;
>       }
>   
> -    if (vfio_viommu_preset(vbasedev)) {
> +    if (!vfio_device_dirty_pages_disabled(vbasedev) &&
> +        vfio_viommu_preset(vbasedev)) {
>           error_setg(&err, "%s: Migration is currently not supported "
>                      "with vIOMMU enabled", vbasedev->name);
>           goto add_blocker;