netdev - Re: [PATCH net-next v6 1/4] hv_sock: Return the readable bytes in hvs_stream_has

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Message-ID: <aG755Yx-FVKIkHzH@liuwe-devbox-ubuntu-v2.lamzopl0uupeniq2etz1fddiyg.xx.internal.cloudapp.net>
Date: Wed, 9 Jul 2025 23:23:17 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Xuewei Niu <niuxuewei.nxw@...group.com>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, linux-hyperv@...r.kernel.org,
	virtualization@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, niuxuewei97@...il.com
Subject: Re: [PATCH net-next v6 1/4] hv_sock: Return the readable bytes in
 hvs_stream_has_data()

On Tue, Jul 08, 2025 at 02:36:11PM +0800, Xuewei Niu wrote:
> From: Dexuan Cui <decui@...rosoft.com>
> 
> When hv_sock was originally added, __vsock_stream_recvmsg() and
> vsock_stream_has_data() actually only needed to know whether there
> is any readable data or not, so hvs_stream_has_data() was written to
> return 1 or 0 for simplicity.
> 
> However, now hvs_stream_has_data() should return the readable bytes
> because vsock_data_ready() -> vsock_stream_has_data() needs to know the
> actual bytes rather than a boolean value of 1 or 0.
> 
> The SIOCINQ ioctl support also needs hvs_stream_has_data() to return
> the readable bytes.
> 
> Let hvs_stream_has_data() return the readable bytes of the payload in
> the next host-to-guest VMBus hv_sock packet.
> 
> Note: there may be multiple incoming hv_sock packets pending in the
> VMBus channel's ringbuffer, but so far there is not a VMBus API that
> allows us to know all the readable bytes in total without reading and
> caching the payload of the multiple packets, so let's just return the
> readable bytes of the next single packet. In the future, we'll either
> add a VMBus API that allows us to know the total readable bytes without
> touching the data in the ringbuffer, or the hv_sock driver needs to
> understand the VMBus packet format and parse the packets directly.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Signed-off-by: Xuewei Niu <niuxuewei.nxw@...group.com>

Acked-by: Wei Liu <wei.liu@...nel.org>