Re: [dpdk-dev] [PATCH v6 04/10] vhost: add two new messages to support a shared buffer

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 8/29/19 4:12 PM, JinYu wrote:
> This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> and VHOST_USER_SET_INFLIGHT_FD to support transferring a shared
> buffer between qemu and backend.
> 
> Signed-off-by: Lin Li <lilin24@baidu.com>
> Signed-off-by: Xun Ni <nixun@baidu.com>
> Signed-off-by: Yu Zhang <zhangyu31@baidu.com>
> Signed-off-by: Jin Yu <jin.yu@intel.com>
> ---
>  lib/librte_vhost/vhost.h      |   7 +
>  lib/librte_vhost/vhost_user.c | 242 ++++++++++++++++++++++++++++++++++
>  lib/librte_vhost/vhost_user.h |   4 +-
>  3 files changed, 252 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 884befa85..39f645b97 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -286,6 +286,12 @@ struct guest_page {
>  	uint64_t size;
>  };
>  
> +struct inflight_mem_info {
> +	int		fd;
> +	void		*addr;
> +	uint64_t	size;
> +};
> +
>  /**
>   * Device structure contains all configuration information relating
>   * to the device.
> @@ -303,6 +309,7 @@ struct virtio_net {
>  	uint32_t		nr_vring;
>  	int			dequeue_zero_copy;
>  	struct vhost_virtqueue	*virtqueue[VHOST_MAX_QUEUE_PAIRS * 2];
> +	struct inflight_mem_info inflight_info;

Could it be a pointer and allocated only if the feature
has been negotiated?

>  #define IF_NAME_SZ (PATH_MAX > IFNAMSIZ ? PATH_MAX : IFNAMSIZ)
>  	char			ifname[IF_NAME_SZ];
>  	uint64_t		log_size;
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index c9e29ece8..647929234 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -49,6 +49,15 @@
>  #define VIRTIO_MIN_MTU 68
>  #define VIRTIO_MAX_MTU 65535
>  
> +#define INFLIGHT_ALIGNMENT	64
> +#define INFLIGHT_VERSION	0xabcd
> +#define VIRTQUEUE_MAX_SIZE	1024
> +
> +#define CLOEXEC		0x0001U
> +
> +#define ALIGN_DOWN(n, m) ((n) / (m) * (m))
> +#define ALIGN_UP(n, m) ALIGN_DOWN((n) + (m) - 1, (m))
> +
>  static const char *vhost_message_str[VHOST_USER_MAX] = {
>  	[VHOST_USER_NONE] = "VHOST_USER_NONE",
>  	[VHOST_USER_GET_FEATURES] = "VHOST_USER_GET_FEATURES",
> @@ -78,6 +87,8 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
>  	[VHOST_USER_POSTCOPY_ADVISE]  = "VHOST_USER_POSTCOPY_ADVISE",
>  	[VHOST_USER_POSTCOPY_LISTEN]  = "VHOST_USER_POSTCOPY_LISTEN",
>  	[VHOST_USER_POSTCOPY_END]  = "VHOST_USER_POSTCOPY_END",
> +	[VHOST_USER_GET_INFLIGHT_FD] = "VHOST_USER_GET_INFLIGHT_FD",
> +	[VHOST_USER_SET_INFLIGHT_FD] = "VHOST_USER_SET_INFLIGHT_FD",
>  };
>  
>  static int send_vhost_reply(int sockfd, struct VhostUserMsg *msg);
> @@ -160,6 +171,16 @@ vhost_backend_cleanup(struct virtio_net *dev)
>  		dev->log_addr = 0;
>  	}
>  
> +	if (dev->inflight_info.addr) {
> +		munmap(dev->inflight_info.addr, dev->inflight_info.size);
> +		dev->inflight_info.addr = NULL;
> +	}
> +
> +	if (dev->inflight_info.fd > 0) {
> +		close(dev->inflight_info.fd);
> +		dev->inflight_info.fd = -1;
> +	}
> +
>  	if (dev->slave_req_fd >= 0) {
>  		close(dev->slave_req_fd);
>  		dev->slave_req_fd = -1;
> @@ -1165,6 +1186,225 @@ virtio_is_ready(struct virtio_net *dev)
>  	return 1;
>  }
>  
> +static int
> +mem_create(const char *name, unsigned int flags)
> +{
> +#ifdef __NR_memfd_create
> +	return syscall(__NR_memfd_create, name, flags);
> +#else
> +	return -1;
> +#endif
> +}

Maybe you could use memfd_create, as done in:
lib/librte_eal/linux/eal/eal_memalloc.c