Re: [PATCH v1 08/17] migration/colo: Use ram_block_discard_set_broken()

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
	qemu-s390x@nongnu.org, Richard Henderson <rth@twiddle.net>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Hailiang Zhang <zhang.zhanghailiang@huawei.com>,
	Juan Quintela <quintela@redhat.com>
Subject: Re: [PATCH v1 08/17] migration/colo: Use ram_block_discard_set_broken()
Date: Fri, 15 May 2020 14:58:41 +0100	[thread overview]
Message-ID: <20200515135841.GF2954@work-vm> (raw)
In-Reply-To: <20200506094948.76388-9-david@redhat.com>

* David Hildenbrand (david@redhat.com) wrote:
> COLO will copy all memory in a RAM block, mark discarding of RAM broken.
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Hailiang Zhang <zhang.zhanghailiang@huawei.com>
> Cc: Juan Quintela <quintela@redhat.com>
> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  include/migration/colo.h |  2 +-
>  migration/migration.c    |  8 +++++++-
>  migration/savevm.c       | 11 +++++++++--
>  3 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/include/migration/colo.h b/include/migration/colo.h
> index 1636e6f907..768e1f04c3 100644
> --- a/include/migration/colo.h
> +++ b/include/migration/colo.h
> @@ -25,7 +25,7 @@ void migrate_start_colo_process(MigrationState *s);
>  bool migration_in_colo_state(void);
>  
>  /* loadvm */
> -void migration_incoming_enable_colo(void);
> +int migration_incoming_enable_colo(void);
>  void migration_incoming_disable_colo(void);
>  bool migration_incoming_colo_enabled(void);
>  void *colo_process_incoming_thread(void *opaque);
> diff --git a/migration/migration.c b/migration/migration.c
> index 177cce9e95..f6830e4620 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -338,12 +338,18 @@ bool migration_incoming_colo_enabled(void)
>  
>  void migration_incoming_disable_colo(void)
>  {
> +    ram_block_discard_set_broken(false);
>      migration_colo_enabled = false;
>  }
>  
> -void migration_incoming_enable_colo(void)
> +int migration_incoming_enable_colo(void)
>  {
> +    if (ram_block_discard_set_broken(true)) {
> +        error_report("COLO: cannot set discarding of RAM broken");

I'd prefer 'COLO: cannot disable RAM discard'

'broken' suggests the user has to go and fix something or report a bug
or something.

Other than that:

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Dave

> +        return -EBUSY;
> +    }
>      migration_colo_enabled = true;
> +    return 0;
>  }
>  
>  void migrate_add_address(SocketAddress *address)
> diff --git a/migration/savevm.c b/migration/savevm.c
> index c00a6807d9..19b4f9600d 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2111,8 +2111,15 @@ static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
>  
>  static int loadvm_process_enable_colo(MigrationIncomingState *mis)
>  {
> -    migration_incoming_enable_colo();
> -    return colo_init_ram_cache();
> +    int ret = migration_incoming_enable_colo();
> +
> +    if (!ret) {
> +        ret = colo_init_ram_cache();
> +        if (ret) {
> +            migration_incoming_disable_colo();
> +        }
> +    }
> +    return ret;
>  }
>  
>  /*
> -- 
> 2.25.3
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK