Re: [PATCH v5 31/36] vfio/migration: Add x-migration-multifd-transfer VFIO property

["Cédric Le Goater" <clg@redhat.com>]

On 2/19/25 21:34, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
> 
> This property allows configuring at runtime whether to transfer the
> particular device state via multifd channels when live migrating that
> device.
> 
> It defaults to AUTO, which means that VFIO device state transfer via
> multifd channels is attempted in configurations that otherwise support it.
> 
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
> ---
>   hw/vfio/migration-multifd.c   | 17 ++++++++++++++++-
>   hw/vfio/pci.c                 |  3 +++
>   include/hw/vfio/vfio-common.h |  2 ++
>   3 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c
> index 0cfa9d31732a..18a5ff964a37 100644
> --- a/hw/vfio/migration-multifd.c
> +++ b/hw/vfio/migration-multifd.c
> @@ -460,11 +460,26 @@ bool vfio_multifd_transfer_supported(void)
>   
>   bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev)
>   {
> -    return false;
> +    VFIOMigration *migration = vbasedev->migration;
> +
> +    return migration->multifd_transfer;
>   }
>   
>   bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp)
>   {
> +    VFIOMigration *migration = vbasedev->migration;
> +
> +    /*
> +     * Make a copy of this setting at the start in case it is changed
> +     * mid-migration.
> +     */
> +    if (vbasedev->migration_multifd_transfer == ON_OFF_AUTO_AUTO) {
> +        migration->multifd_transfer = vfio_multifd_transfer_supported();
> +    } else {
> +        migration->multifd_transfer =
> +            vbasedev->migration_multifd_transfer == ON_OFF_AUTO_ON;
> +    }
> +
>       if (vfio_multifd_transfer_enabled(vbasedev) &&
>           !vfio_multifd_transfer_supported()) {
>           error_setg(errp,
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 89d900e9cf0c..184ff882f9d1 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -3377,6 +3377,9 @@ static const Property vfio_pci_dev_properties[] = {
>                       VFIO_FEATURE_ENABLE_IGD_OPREGION_BIT, false),
>       DEFINE_PROP_ON_OFF_AUTO("enable-migration", VFIOPCIDevice,
>                               vbasedev.enable_migration, ON_OFF_AUTO_AUTO),
> +    DEFINE_PROP_ON_OFF_AUTO("x-migration-multifd-transfer", VFIOPCIDevice,
> +                            vbasedev.migration_multifd_transfer,
> +                            ON_OFF_AUTO_AUTO),
>       DEFINE_PROP_BOOL("migration-events", VFIOPCIDevice,
>                        vbasedev.migration_events, false),
>       DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false),

Please add property documentation in vfio_pci_dev_class_init()


Thanks,

C.



> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index ba851917f9fc..3006931accf6 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -91,6 +91,7 @@ typedef struct VFIOMigration {
>       uint64_t mig_flags;
>       uint64_t precopy_init_size;
>       uint64_t precopy_dirty_size;
> +    bool multifd_transfer;
>       VFIOMultifd *multifd;
>       bool initial_data_sent;
>   
> @@ -153,6 +154,7 @@ typedef struct VFIODevice {
>       bool no_mmap;
>       bool ram_block_discard_allowed;
>       OnOffAuto enable_migration;
> +    OnOffAuto migration_multifd_transfer;
>       bool migration_events;
>       VFIODeviceOps *ops;
>       unsigned int num_irqs;
>