Re: [Qemu-devel] [PATCH v3 10/29] vhost+postcopy: Register shared ufd with postcopy

[Peter Xu]

On Fri, Feb 16, 2018 at 01:16:06PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> Register the UFD that comes in as the response to the 'advise' method
> with the postcopy code.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  hw/virtio/vhost-user.c   | 21 ++++++++++++++++++++-
>  migration/postcopy-ram.h |  2 +-
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 4f59993baa..dd4eb50668 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -24,6 +24,7 @@
>  #include <sys/socket.h>
>  #include <sys/un.h>
>  #include <linux/vhost.h>
> +#include <linux/userfaultfd.h>

Why this line?

>  
>  #define VHOST_MEMORY_MAX_NREGIONS    8
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
> @@ -155,6 +156,7 @@ struct vhost_user {
>      CharBackend *chr;
>      int slave_fd;
>      NotifierWithReturn postcopy_notifier;
> +    struct PostCopyFD  postcopy_fd;
>  };
>  
>  static bool ioeventfd_enabled(void)
> @@ -780,6 +782,17 @@ out:
>      return ret;
>  }
>  
> +/*
> + * Called back from the postcopy fault thread when a fault is received on our
> + * ufd.
> + * TODO: This is Linux specific
> + */
> +static int vhost_user_postcopy_fault_handler(struct PostCopyFD *pcfd,
> +                                             void *ufd)
> +{
> +    return 0;
> +}
> +
>  /*
>   * Called at the start of an inbound postcopy on reception of the
>   * 'advise' command.
> @@ -819,8 +832,14 @@ static int vhost_user_postcopy_advise(struct vhost_dev 
> *dev, Error **errp)
>          error_setg(errp, "%s: Failed to get ufd", __func__);
>          return -1;
>      }
> +    fcntl(ufd, F_SETFL, O_NONBLOCK);

Only curious: would it work even without this line?

>  
> -    /* TODO: register ufd with userfault thread */
> +    /* register ufd with userfault thread */
> +    u->postcopy_fd.fd = ufd;
> +    u->postcopy_fd.data = dev;
> +    u->postcopy_fd.handler = vhost_user_postcopy_fault_handler;
> +    u->postcopy_fd.idstr = "vhost-user"; /* Need to find unique name */
> +    postcopy_register_shared_ufd(&u->postcopy_fd);
>      return 0;
>  }
>  
> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> index 4bda5aa509..23efbdf346 100644
> --- a/migration/postcopy-ram.h
> +++ b/migration/postcopy-ram.h
> @@ -153,7 +153,7 @@ struct PostCopyFD {
>      /* Handler to be called whenever we get a poll event */
>      pcfdhandler handler;
>      /* A string to use in error messages */
> -    char *idstr;
> +    const char *idstr;

Move to previous patch?

>  };
>  
>  /* Register a userfaultfd owned by an external process for
> -- 
> 2.14.3
> 

-- 
Peter Xu