netdev - Re: [PATCH] vdpa: bypass waking up vhost

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Date:   Tue, 2 Jun 2020 12:42:03 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Zhu Lingshan <lingshan.zhu@...el.com>,
        mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        jasowang@...hat.com
Cc:     lkp@...el.com, kbuild-all@...ts.01.org, lulu@...hat.com,
        dan.daly@...el.com, cunming.liang@...el.com,
        Zhu Lingshan <lingshan.zhu@...el.com>
Subject: Re: [PATCH] vdpa: bypass waking up vhost_woker for vdpa vq kick

Hi Zhu,

url:    https://github.com/0day-ci/linux/commits/Zhu-Lingshan/vdpa-bypass-waking-up-vhost_woker-for-vdpa-vq-kick/20200526-133819
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
config: x86_64-randconfig-m001-20200529 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
drivers/vhost/vdpa.c:348 vhost_vdpa_set_vring_kick() error: uninitialized symbol 'r'.

# https://github.com/0day-ci/linux/commit/a84ddbf1ef29f18aafb2bb8a93bcedd4a29a967d
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout a84ddbf1ef29f18aafb2bb8a93bcedd4a29a967d
vim +/r +348 drivers/vhost/vdpa.c

a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  316  static long vhost_vdpa_set_vring_kick(struct vhost_virtqueue *vq,
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  317  				      void __user *argp)
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  318  {
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  319  	bool pollstart = false, pollstop = false;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  320  	struct file *eventfp, *filep = NULL;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  321  	struct vhost_vring_file f;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  322  	long r;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  323  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  324  	if (copy_from_user(&f, argp, sizeof(f)))
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  325  		return -EFAULT;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  326  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  327  	eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  328  	if (IS_ERR(eventfp)) {
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  329  		r = PTR_ERR(eventfp);
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  330  		return r;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  331  	}
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  332  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  333  	if (eventfp != vq->kick) {
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  334  		pollstop = (filep = vq->kick) != NULL;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  335  		pollstart = (vq->kick = eventfp) != NULL;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  336  	} else
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  337  		filep = eventfp;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  338  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  339  	if (pollstop && vq->handle_kick)
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  340  		vhost_vdpa_poll_stop(vq);
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  341  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  342  	if (filep)
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  343  		fput(filep);
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  344  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  345  	if (pollstart && vq->handle_kick)
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  346  		r = vhost_vdpa_poll_start(vq);

"r" not initialized on else path.

a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  347  
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26 @348  	return r;
a84ddbf1ef29f1 Zhu Lingshan 2020-05-26  349  }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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