Re: [Qemu-devel] [RFC PATCH] configure: remove --enable-replication/--disable-replication

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/02/2017 07:00, Stefan Hajnoczi wrote:
> On Thu, Feb 02, 2017 at 07:05:30AM -0800, Paolo Bonzini wrote:
>> The replication feature is a small amount of code, does not
>> require any external library and unless used does not add
>> anything to the guest's attack surface.  Since any extra
>> configure option affects maintainability on the other hand
>> and is subject to bit rot, I think there is no need to
>> make it configurable.
> 
> I think the current state is good: replication is enabled by default but
> can be compiled out if desired.
> 
> Downstreams may not be comfortable supporting this feature yet since
> it's incomplete.  It's fair to offer an option to disable it, otherwise
> downstreams will have to patch this themselves.

I understand---I just am not sure where to draw the line because there's
plenty of other incomplete features, hence the RFC.  For example,
record/replay cannot be enabled or disabled on the configure command
line.  That was the case even in the beginning, where it didn't support
either block or character device replay.

--enable-coroutine-pool is a relic of when Windows builds needed it, but
all other --enable-* options require an external library or at least a
specific operating system.  See for example this patch:

    commit 52b53c04faab9f7a9879c8dc014930649a3e698d
    Author: Fam Zheng <famz@redhat.com>
    Date:   Wed Sep 10 14:17:51 2014 +0800

    block: Always compile virtio-blk dataplane

    Dataplane doesn't depend on linux-aio any more, so we don't need the
    compiling condition now.

    Configure options are kept but just print a message.

    Signed-off-by: Fam Zheng <famz@redhat.com>
    Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
    Message-id: 1410329871-28885-4-git-send-email-famz@redhat.com
    Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>


I would actually prefer to remove many of the latter
(--enable-vhost-net, --enable-vhost-scsi, --enable-vhost-socket) and
just use default-configs.  We are already doing it for ivshmem for example:

    CONFIG_IVSHMEM=$(CONFIG_EVENTFD)

Paolo