Re: [PULL 15/21] migration/rdma: Remove all uses of RAM_CONTROL_HOOK

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, May 30, 2023 at 08:25:25PM +0200, Juan Quintela wrote:
> Instead of going trhough ram_control_load_hook(), call
> qemu_rdma_registration_handle() directly.
> 
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> Message-Id: <20230509120700.78359-5-quintela@redhat.com>
> ---
>  migration/qemu-file.h | 1 -
>  migration/rdma.h      | 3 +++
>  migration/ram.c       | 5 ++++-
>  migration/rdma.c      | 9 +++++----
>  4 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index 323af5682f..7cfc20825e 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -41,7 +41,6 @@ typedef int (QEMURamHookFunc)(QEMUFile *f, uint64_t flags, void *data);
>   */
>  #define RAM_CONTROL_SETUP     0
>  #define RAM_CONTROL_ROUND     1
> -#define RAM_CONTROL_HOOK      2
>  #define RAM_CONTROL_FINISH    3
>  #define RAM_CONTROL_BLOCK_REG 4
>  
> diff --git a/migration/rdma.h b/migration/rdma.h
> index c13b94c782..8bd277efb9 100644
> --- a/migration/rdma.h
> +++ b/migration/rdma.h
> @@ -24,10 +24,13 @@ void rdma_start_incoming_migration(const char *host_port, Error **errp);
>  
>  
>  #ifdef CONFIG_RDMA
> +int qemu_rdma_registration_handle(QEMUFile *f);
>  int qemu_rdma_registration_start(QEMUFile *f, uint64_t flags);
>  int qemu_rdma_registration_stop(QEMUFile *f, uint64_t flags);
>  #else
>  static inline
> +int qemu_rdma_registration_handle(QEMUFile *f) { return 0; }
> +static inline
>  int qemu_rdma_registration_start(QEMUFile *f, uint64_t flags) { return 0; }
>  static inline
>  int qemu_rdma_registration_stop(QEMUFile *f, uint64_t flags) { return 0; }
> diff --git a/migration/ram.c b/migration/ram.c
> index c6fad7b0b3..6f0597814c 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -4024,7 +4024,10 @@ static int ram_load_precopy(QEMUFile *f)
>              }
>              break;
>          case RAM_SAVE_FLAG_HOOK:
> -            ram_control_load_hook(f, RAM_CONTROL_HOOK, NULL);
> +            ret = qemu_rdma_registration_handle(f);
> +            if (ret < 0) {
> +                qemu_file_set_error(f, ret);
> +            }
>              break;
>          default:
>              error_report("Unknown combination of migration flags: 0x%x", flags);
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 8001dcb960..a477985c6d 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -3530,7 +3530,7 @@ static int dest_ram_sort_func(const void *a, const void *b)
>   *
>   * Keep doing this until the source tells us to stop.
>   */
> -static int qemu_rdma_registration_handle(QEMUFile *f)
> +int qemu_rdma_registration_handle(QEMUFile *f)
>  {
>      RDMAControlHeader reg_resp = { .len = sizeof(RDMARegisterResult),
>                                 .type = RDMA_CONTROL_REGISTER_RESULT,
> @@ -3557,6 +3557,10 @@ static int qemu_rdma_registration_handle(QEMUFile *f)

A few lines above this diff contxt there is a call to

    QIOChannelRDMA *rioc = QIO_CHANNEL_RDMA(qemu_file_get_ioc(f));

which is likely unsafe given that....

>      int count = 0;
>      int i = 0;
>  
> +    if (!migrate_rdma()) {

....we're only checking if this is RDMA here.

> +        return 0;
> +    }
> +
>      RCU_READ_LOCK_GUARD();
>      rdma = qatomic_rcu_read(&rioc->rdmain);
>  

With regards,
Daniel
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