Re: [Qemu-devel] [RFC 29/29] vhost-user: Claim support for postcopy

[Maxime Coquelin]

On 06/28/2017 09:00 PM, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Tell QEMU we understand the protocol features needed for postcopy.
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>   contrib/libvhost-user/libvhost-user.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/contrib/libvhost-user/libvhost-user.c 
> b/contrib/libvhost-user/libvhost-user.c
> index c1716d1a62..1c46aecfb3 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -797,7 +797,8 @@ vu_set_vring_err_exec(VuDev *dev, VhostUserMsg *vmsg)
>   static bool
>   vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
>   {
> -    uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD;
> +    uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD |
> +                        1ULL << VHOST_USER_PROTOCOL_F_POSTCOPY;

Maybe advertising VHOST_USER_PROTOCOL_F_POSTCOPY could be done only
if userfaultfd syscall is supported?

>   
>       if (dev->iface->get_protocol_features) {
>           features |= dev->iface->get_protocol_features(dev);