linux-kernel - Re: [Patch net v3] vsock/virtio: fix variables initialization during resuming

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Message-ID: <7zof7x3scn2jlszxwynyaw3i5lcwfo5j3yrgw2sraq6pw545h5@zwoqaewlq2m4>
Date: Fri, 14 Feb 2025 14:34:40 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Junnan Wu <junnan01.wu@...sung.com>
Cc: davem@...emloft.net, edumazet@...gle.com, eperezma@...hat.com, 
	horms@...nel.org, jasowang@...hat.com, kuba@...nel.org, kvm@...r.kernel.org, 
	lei19.wang@...sung.com, linux-kernel@...r.kernel.org, mst@...hat.com, 
	netdev@...r.kernel.org, pabeni@...hat.com, q1.huang@...sung.com, stefanha@...hat.com, 
	virtualization@...ts.linux.dev, xuanzhuo@...ux.alibaba.com, ying01.gao@...sung.com, 
	ying123.xu@...sung.com
Subject: Re: [Patch net v3] vsock/virtio: fix variables initialization during
 resuming

On Fri, Feb 14, 2025 at 09:22:00AM +0800, Junnan Wu wrote:
>When executing suspend to ram twice in a row,
>the `rx_buf_nr` and `rx_buf_max_nr` increase to three times vq->num_free.
>Then after virtqueue_get_buf and `rx_buf_nr` decreased
>in function virtio_transport_rx_work,
>the condition to fill rx buffer
>(rx_buf_nr < rx_buf_max_nr / 2) will never be met.
>
>It is because that `rx_buf_nr` and `rx_buf_max_nr`
>are initialized only in virtio_vsock_probe(),
>but they should be reset whenever virtqueues are recreated,
>like after a suspend/resume.
>
>Move the `rx_buf_nr` and `rx_buf_max_nr` initialization in
>virtio_vsock_vqs_init(), so we are sure that they are properly
>initialized, every time we initialize the virtqueues, either when we
>load the driver or after a suspend/resume.
>
>To prevent erroneous atomic load operations on the `queued_replies`
>in the virtio_transport_send_pkt_work() function
>which may disrupt the scheduling of vsock->rx_work
>when transmitting reply-required socket packets,
>this atomic variable must undergo synchronized initialization
>alongside the preceding two variables after a suspend/resume.
>
>Fixes: bd50c5dc182b ("vsock/virtio: add support for device suspend/resume")
>Link: https://lore.kernel.org/virtualization/20250207052033.2222629-1-junnan01.wu@samsung.com/
>Co-developed-by: Ying Gao <ying01.gao@...sung.com>
>Signed-off-by: Ying Gao <ying01.gao@...sung.com>
>Signed-off-by: Junnan Wu <junnan01.wu@...sung.com>
>---
> net/vmw_vsock/virtio_transport.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>