Re: [Qemu-devel] [PATCH v8 06/11] migration: add postcopy blocktime ctx into MigrationIncomingState

[Juan Quintela <quintela@redhat.com>]

Alexey Perevalov <a.perevalov@samsung.com> wrote:
> This patch adds request to kernel space for UFFD_FEATURE_THREAD_ID,
> in case when this feature is provided by kernel.
>

I think this function is wrong

> +static void migration_exit_cb(Notifier *n, void *data)
> +{
> +    PostcopyBlocktimeContext *ctx = container_of(n, PostcopyBlocktimeContext,
> +                                                 exit_notifier);
> +    destroy_blocktime_context(ctx);
> +}
> +
> +static struct PostcopyBlocktimeContext *blocktime_context_new(void)
> +{
> +    PostcopyBlocktimeContext *ctx = g_new0(PostcopyBlocktimeContext, 1);
> +    ctx->page_fault_vcpu_time = g_new0(int64_t, smp_cpus);
> +    ctx->vcpu_addr = g_new0(uint64_t, smp_cpus);
> +    ctx->vcpu_blocktime = g_new0(int64_t, smp_cpus);
> +
> +    ctx->exit_notifier.notify = migration_exit_cb;
> +    qemu_add_exit_notifier(&ctx->exit_notifier);
> +    add_migration_state_change_notifier(&ctx->postcopy_notifier);

Or you don't want to call it this awy.

This will destroy the context at every migration state change.

Or I am missing something here?  Look at ui/spice-core.c to see how to
use it only for some states (I guess you will need to do it for
error/cleanup/completion changes only).

Later, Juan.

> +    return ctx;
> +}
>  
>  /**
>   * receive_ufd_features: check userfault fd features, to request only supported
> @@ -155,6 +207,19 @@ static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis)
>          }
>      }
>  
> +#ifdef UFFD_FEATURE_THREAD_ID
> +    if (migrate_postcopy_blocktime() && mis &&
> +        UFFD_FEATURE_THREAD_ID & supported_features) {
> +        /* kernel supports that feature */
> +        /* don't create blocktime_context if it exists */
> +        if (!mis->blocktime_ctx) {
> +            mis->blocktime_ctx = blocktime_context_new();
> +        }
> +
> +        asked_features |= UFFD_FEATURE_THREAD_ID;
> +    }
> +#endif
> +
>      /*
>       * request features, even if asked_features is 0, due to
>       * kernel expects UFFD_API before UFFDIO_REGISTER, per