Re: [PATCH v5 25/36] vfio/migration: Multifd device state transfer support - receive init/cleanup

["Cédric Le Goater" <clg@redhat.com>]

On 2/26/25 11:14, Cédric Le Goater wrote:
> On 2/19/25 21:34, Maciej S. Szmigiero wrote:
>> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
>>
>> Add support for VFIOMultifd data structure that will contain most of the
>> receive-side data together with its init/cleanup methods.
>>
>> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
>> ---
>>   hw/vfio/migration-multifd.c   | 33 +++++++++++++++++++++++++++++++++
>>   hw/vfio/migration-multifd.h   |  8 ++++++++
>>   hw/vfio/migration.c           | 29 +++++++++++++++++++++++++++--
>>   include/hw/vfio/vfio-common.h |  3 +++
>>   4 files changed, 71 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c
>> index 7328ad8e925c..c2defc0efef0 100644
>> --- a/hw/vfio/migration-multifd.c
>> +++ b/hw/vfio/migration-multifd.c
>> @@ -41,6 +41,9 @@ typedef struct VFIOStateBuffer {
>>       size_t len;
>>   } VFIOStateBuffer;
>> +typedef struct VFIOMultifd {
>> +} VFIOMultifd;
>> +
>>   static void vfio_state_buffer_clear(gpointer data)
>>   {
>>       VFIOStateBuffer *lb = data;
>> @@ -84,8 +87,38 @@ static VFIOStateBuffer *vfio_state_buffers_at(VFIOStateBuffers *bufs, guint idx)
>>       return &g_array_index(bufs->array, VFIOStateBuffer, idx);
>>   }
>> +VFIOMultifd *vfio_multifd_new(void)
>> +{
>> +    VFIOMultifd *multifd = g_new(VFIOMultifd, 1);
>> +
>> +    return multifd;
>> +}
>> +
>> +void vfio_multifd_free(VFIOMultifd *multifd)
>> +{
>> +    g_free(multifd);
>> +}
>> +
>>   bool vfio_multifd_transfer_supported(void)
>>   {
>>       return multifd_device_state_supported() &&
>>           migrate_send_switchover_start();
>>   }
>> +
>> +bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev)
>> +{
>> +    return false;
>> +}
>> +
>> +bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp)
>> +{
>> +    if (vfio_multifd_transfer_enabled(vbasedev) &&
>> +        !vfio_multifd_transfer_supported()) {
>> +        error_setg(errp,
>> +                   "%s: Multifd device transfer requested but unsupported in the current config",
>> +                   vbasedev->name);
>> +        return false;
>> +    }


now that I have reached patch 31 I understand better. I would put the
check above in patch 31 and simply return true for now.

Thanks,

C.


>> +    return true;
>> +}
>> diff --git a/hw/vfio/migration-multifd.h b/hw/vfio/migration-multifd.h
>> index 8fe004c1da81..1eefba3b2eed 100644
>> --- a/hw/vfio/migration-multifd.h
>> +++ b/hw/vfio/migration-multifd.h
>> @@ -12,6 +12,14 @@
>>   #include "hw/vfio/vfio-common.h"
>> +typedef struct VFIOMultifd VFIOMultifd;
>> +
>> +VFIOMultifd *vfio_multifd_new(void);
>> +void vfio_multifd_free(VFIOMultifd *multifd);
>> +
>>   bool vfio_multifd_transfer_supported(void);
>> +bool vfio_multifd_transfer_enabled(VFIODevice *vbasedev);
>> +
>> +bool vfio_multifd_transfer_setup(VFIODevice *vbasedev, Error **errp);
>>   #endif
>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>> index 7b79be6ad293..4311de763885 100644
>> --- a/hw/vfio/migration.c
>> +++ b/hw/vfio/migration.c
>> @@ -674,15 +674,40 @@ static void vfio_save_state(QEMUFile *f, void *opaque)
>>   static int vfio_load_setup(QEMUFile *f, void *opaque, Error **errp)
>>   {
>>       VFIODevice *vbasedev = opaque;
>> +    VFIOMigration *migration = vbasedev->migration;
>> +    int ret;
>> +
>> +    if (!vfio_multifd_transfer_setup(vbasedev, errp)) {
>> +        return -EINVAL;
>> +    }
> 
> This check on the consistency of the settings confused me a little. Even if
> simple, I would have put it in a separate patch for better understanding.
> The rest looks good.
> 
> 
> Thanks,
> 
> C.
> 
> 
> 
>> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
>> +                                   migration->device_state, errp);
>> +    if (ret) {
>> +        return ret;
>> +    }
>> -    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
>> -                                    vbasedev->migration->device_state, errp);
>> +    if (vfio_multifd_transfer_enabled(vbasedev)) {
>> +        assert(!migration->multifd);
>> +        migration->multifd = vfio_multifd_new();
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static void vfio_multifd_cleanup(VFIODevice *vbasedev)
>> +{
>> +    VFIOMigration *migration = vbasedev->migration;
>> +
>> +    g_clear_pointer(&migration->multifd, vfio_multifd_free);
>>   }
>>   static int vfio_load_cleanup(void *opaque)
>>   {
>>       VFIODevice *vbasedev = opaque;
>> +    vfio_multifd_cleanup(vbasedev);
>> +
>>       vfio_migration_cleanup(vbasedev);
>>       trace_vfio_load_cleanup(vbasedev->name);
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index 64ee3b1a2547..ab110198bd6b 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -78,6 +78,8 @@ typedef struct VFIORegion {
>>       uint8_t nr; /* cache the region number for debug */
>>   } VFIORegion;
>> +typedef struct VFIOMultifd VFIOMultifd;
>> +
>>   typedef struct VFIOMigration {
>>       struct VFIODevice *vbasedev;
>>       VMChangeStateEntry *vm_state;
>> @@ -89,6 +91,7 @@ typedef struct VFIOMigration {
>>       uint64_t mig_flags;
>>       uint64_t precopy_init_size;
>>       uint64_t precopy_dirty_size;
>> +    VFIOMultifd *multifd;
>>       bool initial_data_sent;
>>       bool event_save_iterate_started;
>>
>