Re: [PATCH RFC 06/12] migration/rdma: Transmit initial package

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Zhimin Feng (fengzhimin1@huawei.com) wrote:
> From: fengzhimin <fengzhimin1@huawei.com>
> 
> Transmit initial package through the multiRDMA channels,
> so that we can identify the main channel and multiRDMA channels.
> 
> Signed-off-by: fengzhimin <fengzhimin1@huawei.com>

'packet' not 'package'

> ---
>  migration/rdma.c | 114 ++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 107 insertions(+), 7 deletions(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 5b780bef36..db75a4372a 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -116,6 +116,16 @@ static uint32_t known_capabilities = RDMA_CAPABILITY_PIN_ALL;
>  
>  #define RDMA_WRID_CHUNK_MASK (~RDMA_WRID_BLOCK_MASK & ~RDMA_WRID_TYPE_MASK)
>  
> +/* Define magic to distinguish multiRDMA and main RDMA */
> +#define MULTIRDMA_MAGIC 0x11223344U
> +#define MAINRDMA_MAGIC 0x55667788U

Can you explain more about when you use these two - is it 'MAINRDMA' on
the first channel/file and multi on the extra ones???

> +#define ERROR_MAGIC 0xFFFFFFFFU
> +
> +#define MULTIRDMA_VERSION 1
> +#define MAINRDMA_VERSION 1
> +
> +#define UNUSED_ID 0xFFU

Make sure you can't set the number of channels to 256 (or more) then.

>  /*
>   * RDMA migration protocol:
>   * 1. RDMA Writes (data messages, i.e. RAM)
> @@ -167,6 +177,14 @@ enum {
>      RDMA_CONTROL_UNREGISTER_FINISHED, /* unpinning finished */
>  };
>  
> +/*
> + * Identify the MultiRDAM channel info
> + */
> +typedef struct {
> +    uint32_t magic;
> +    uint32_t version;
> +    uint8_t id;
> +} __attribute__((packed)) RDMAChannelInit_t;

Since you're using qemu_get/qemu_put on the QEMUFile, don't
bother with packing a struct, just use qemu_get_be32 and qemu_put_be32.

>  /*
>   * Memory and MR structures used to represent an IB Send/Recv work request.
> @@ -3430,7 +3448,7 @@ static int qemu_rdma_accept(RDMAContext *rdma)
>          int i;
>          RDMAContext *multi_rdma = NULL;
>          thread_count = migrate_multiRDMA_channels();
> -        /* create the multi Thread RDMA channels */
> +        /* create the multiRDMA channels */

That should be fixed in the previous patch that created it.

>          for (i = 0; i < thread_count; i++) {
>              if (multiRDMA_recv_state->params[i].rdma->cm_id == NULL) {
>                  multi_rdma = multiRDMA_recv_state->params[i].rdma;
> @@ -4058,6 +4076,48 @@ static QEMUFile *qemu_fopen_rdma(RDMAContext *rdma, const char *mode)
>      return rioc->file;
>  }
>  
> +static RDMAChannelInit_t migration_rdma_recv_initial_packet(QEMUFile *f,
> +                                                            Error **errp)
> +{
> +    RDMAChannelInit_t msg;
> +    int thread_count = migrate_multiRDMA_channels();
> +    qemu_get_buffer(f, (uint8_t *)&msg, sizeof(msg));
> +    be32_to_cpus(&msg.magic);
> +    be32_to_cpus(&msg.version);
> +
> +    if (msg.magic != MULTIRDMA_MAGIC &&
> +        msg.magic != MAINRDMA_MAGIC) {
> +        error_setg(errp, "multiRDMA: received unrecognized "
> +                   "packet magic %x", msg.magic);
> +        goto err;
> +    }
> +
> +    if (msg.magic == MULTIRDMA_MAGIC
> +        && msg.version != MULTIRDMA_VERSION) {
> +        error_setg(errp, "multiRDMA: received packet version "
> +                   "%d expected %d", msg.version, MULTIRDMA_VERSION);
> +        goto err;
> +    }
> +
> +    if (msg.magic == MAINRDMA_MAGIC && msg.version != MAINRDMA_VERSION) {
> +        error_setg(errp, "multiRDMA: received packet version "
> +                   "%d expected %d", msg.version, MAINRDMA_VERSION);
> +        goto err;
> +    }

It took me a few minutes to see the difference between these two
previous if's the error messages should be different.

> +    if (msg.magic == MULTIRDMA_MAGIC && msg.id > thread_count) {
> +        error_setg(errp, "multiRDMA: received channel version %d "
> +                   "expected %d", msg.version, MULTIRDMA_VERSION);

That text seems wrong, since you're checking for the thread count.

> +        goto err;
> +    }
> +
> +    return msg;
> +err:
> +    msg.magic = ERROR_MAGIC;
> +    msg.id = UNUSED_ID;
> +    return msg;
> +}
> +
>  static void *multiRDMA_recv_thread(void *opaque)
>  {
>      MultiRDMARecvParams *p = opaque;
> @@ -4100,13 +4160,34 @@ static void multiRDMA_recv_new_channel(QEMUFile *f, int id)
>  static void migration_multiRDMA_process_incoming(QEMUFile *f, RDMAContext *rdma)
>  {
>      MigrationIncomingState *mis = migration_incoming_get_current();
> +    Error *local_err = NULL;
> +    RDMAChannelInit_t msg = migration_rdma_recv_initial_packet(f, &local_err);

It's probably simpler here to check for
   if (local_err)

   and then you can avoid the need for ERROR_MAGIC.

> +    switch (msg.magic) {
> +    case MAINRDMA_MAGIC:
> +        if (!mis->from_src_file) {
> +            rdma->migration_started_on_destination = 1;
> +            migration_incoming_setup(f);
> +            migration_incoming_process();
> +        }
> +        break;
>  
> -    if (!mis->from_src_file) {
> -        rdma->migration_started_on_destination = 1;
> -        migration_incoming_setup(f);
> -        migration_incoming_process();
> -    } else {
> -        multiRDMA_recv_new_channel(f, multiRDMA_recv_state->count);
> +    case MULTIRDMA_MAGIC:
> +        multiRDMA_recv_new_channel(f, msg.id);
> +        break;
> +
> +    case ERROR_MAGIC:
> +    default:
> +        if (local_err) {
> +            MigrationState *s = migrate_get_current();
> +            migrate_set_error(s, local_err);
> +            if (s->state == MIGRATION_STATUS_SETUP ||
> +                    s->state == MIGRATION_STATUS_ACTIVE) {
> +                migrate_set_state(&s->state, s->state,
> +                        MIGRATION_STATUS_FAILED);
> +            }
> +        }
> +        break;
>      }
>  }
>  
> @@ -4245,10 +4326,26 @@ err:
>      multiRDMA_load_cleanup();
>  }
>  
> +static void migration_rdma_send_initial_packet(QEMUFile *f, uint8_t id)
> +{
> +    RDMAChannelInit_t msg;
> +
> +    msg.magic = cpu_to_be32(id == UNUSED_ID ?
> +                            MAINRDMA_MAGIC : MULTIRDMA_MAGIC);
> +    msg.version = cpu_to_be32(id == UNUSED_ID ?
> +                              MAINRDMA_VERSION : MULTIRDMA_VERSION);
> +    msg.id = id;
> +    qemu_put_buffer(f, (uint8_t *)&msg, sizeof(msg));
> +    qemu_fflush(f);
> +}
> +
>  static void *multiRDMA_send_thread(void *opaque)
>  {
>      MultiRDMASendParams *p = opaque;
>  
> +    /* send the multiRDMA channels magic */
> +    migration_rdma_send_initial_packet(p->file, p->id);
> +
>      while (true) {
>          qemu_mutex_lock(&p->mutex);
>          if (p->quit) {
> @@ -4579,6 +4676,9 @@ void rdma_start_outgoing_migration(void *opaque,
>      s->to_dst_file = qemu_fopen_rdma(rdma, "wb");
>      /* create multiRDMA channel */
>      if (migrate_use_multiRDMA()) {
> +        /* send the main RDMA channel magic */
> +        migration_rdma_send_initial_packet(s->to_dst_file, UNUSED_ID);
> +
>          if (multiRDMA_save_setup(host_port, errp) != 0) {
>              ERROR(errp, "init multiRDMA channels failure!");
>              goto err;
> -- 
> 2.19.1
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK