Re: [Qemu-devel] [PATCH v2 2/8] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE

[Stefan Hajnoczi]

On Wed, Nov 21, 2012 at 7:17 PM, mdroth <address@hidden> wrote:
> On Tue, Nov 20, 2012 at 01:31:46PM +0100, Stefan Hajnoczi wrote:
>> @@ -2233,6 +2238,17 @@ EOF
>>  fi
>>
>>  ##########################################
>> +# adjust virtio-blk-data-plane based on linux-aio
>> +
>> +if test "$virtio_blk_data_plane" = "yes" -a \
>> +     "$linux_aio" != "yes" ; then
>> +  echo "Error: virtio-blk-data-plane requires Linux AIO, please try 
>> --enable-linux-aio"
>> +  exit 1
>> +elif test -z "$virtio_blk_data_plane" ; then
>> +  virtio_blk_data_plane=$linux_aio
>> +fi
>
> $linux_aio gets set automatically if the user has libaio installed and
> doesn't specify --disable-linux-aio, so this ends up enabling dataplane by
> default in a lot of situations. Since it's experimental I think it should only
> be enabled if we pass --enable-virtio-blk-data-plane explicitly.

I expect downstreams to enable this feature.  Requiring package
maintainers to add --enable-virtio-blk-data-one explicitly is probably
going to cause more work than any benefits of disabling it by default.

The feature has no effect unless -device
virtio-blk-pci,x-data-plane-on is used.  Code size is <12 KB on x86_64
and contains nothing especially risky from a security perspective.

That said, if there is a strong feeling this should be disabled by
default, I can switch it to default off.

Stefan