Subject: Re: [PATCH v8 net-next 1/1] hv_sock: introduce Hyper-V Sockets

From: Joe Perches <[email-masked]>
Date: Thu, 07 Apr 2016 18:15:09 -0700

On Thu, 2016-04-07 at 18:36 -0700, Dexuan Cui wrote:
> Hyper-V Sockets (hv_sock) supplies a byte-stream based communication
> mechanism between the host and the guest. It's somewhat like TCP over
> VMBus, but the transportation layer (VMBus) is much simpler than IP.
[]
> diff --git a/include/net/af_hvsock.h b/include/net/af_hvsock.h
[]
> +#define VMBUS_RINGBUFFER_SIZE_HVSOCK_RECV (5 * PAGE_SIZE)
> +#define VMBUS_RINGBUFFER_SIZE_HVSOCK_SEND (5 * PAGE_SIZE)
> +
> +#define HVSOCK_RCV_BUF_SZ	VMBUS_RINGBUFFER_SIZE_HVSOCK_RECV
> +#define HVSOCK_SND_BUF_SZ	PAGE_SIZE
[]
> +struct hvsock_sock {
[]
> +	struct {
> +		struct vmpipe_proto_header hdr;
> +		char buf[HVSOCK_SND_BUF_SZ];
> +	} __packed send;
> +
> +	struct {
> +		struct vmpipe_proto_header hdr;
> +		char buf[HVSOCK_RCV_BUF_SZ];
> +		unsigned int data_len;
> +		unsigned int data_offset;
> +	} __packed recv;
> +};

These bufs are not page aligned and so can span pages.

Is there any value in allocating these bufs separately
as pages instead of as a kmalloc?