Re: [dpdk-dev] [04/12] vhost: introduce postcopy's advise message

[Ilya Maximets <i.maximets@samsung.com>]

On 27.09.2018 11:28, Ilya Maximets wrote:
> On 26.09.2018 10:26, Maxime Coquelin wrote:
>> This patch opens a userfaultfd and sends it back to Qemu's
>> VHOST_USER_POSTCOPY_ADVISE request.
>>
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>  lib/librte_vhost/vhost.h      |  2 ++
>>  lib/librte_vhost/vhost_user.c | 37 +++++++++++++++++++++++++++++++++++
>>  lib/librte_vhost/vhost_user.h |  3 ++-
>>  3 files changed, 41 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>> index 25ffd7614..21722d8a8 100644
>> --- a/lib/librte_vhost/vhost.h
>> +++ b/lib/librte_vhost/vhost.h
>> @@ -363,6 +363,8 @@ struct virtio_net {
>>  	int			slave_req_fd;
>>  	rte_spinlock_t		slave_req_lock;
>>  
>> +	int			postcopy_ufd;
>> +
>>  	/*
>>  	 * Device id to identify a specific backend device.
>>  	 * It's set to -1 for the default software implementation.
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index a9b429598..bdfe2cac0 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -24,9 +24,13 @@
>>  #include <stdlib.h>
>>  #include <string.h>
>>  #include <unistd.h>
>> +#include <fcntl.h>
>> +#include <linux/userfaultfd.h>
> 
> Maybe we need compile time check for this header existence?
> Otherwise, this will bump minimal kernel version for default linux build
> to something like 4.3.

We'll need a config option here (disabled by default) and guard all
the postcopy related code.
Meson build will be able to detect the header file and enable
the config if possible. Like this:

lib/librte_vhost/meson.build:
if cc.has_header('linux/userfaultfd.h')
       dpdk_conf.set10('RTE_LIBRTE_VHOST_POSTCOPY', true)
endif

Best regards, Ilya Maximets.