Re: [PATCH v6 net-next 4/9] vhost-net: allow configuring extended features

Paolo Abeni
2025-06-27T13:12:00Z

+csky maintainer
On 6/27/25 8:41 AM, kernel test robot wrote:
> Hi Paolo,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on net-next/main]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Paolo-Abeni/scripts-kernel_doc-py-properly-handle-VIRTIO_DECLARE_FEATURES/20250624-221751
> base: net-next/main
> patch link: https://lore.kernel.org/r/23e46bff5333015d92bf0876033750d9fbf555a0.1750753211.git.pabeni%40redhat.com
> patch subject: [PATCH v6 net-next 4/9] vhost-net: allow configuring extended features
> config: csky-randconfig-001-20250627 (https://download.01.org/0day-ci/archive/20250627/202506271443.G9cAx8PS-lkp@intel.com/config)
> compiler: csky-linux-gcc (GCC) 15.1.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250627/202506271443.G9cAx8PS-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202506271443.G9cAx8PS-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/uaccess.h:12,
> from include/linux/sched/task.h:13,
> from include/linux/sched/signal.h:9,
> from include/linux/rcuwait.h:6,
> from include/linux/percpu-rwsem.h:7,
> from include/linux/fs.h:34,
> from include/linux/compat.h:17,
> from drivers/vhost/net.c:8:
> arch/csky/include/asm/uaccess.h: In function '__get_user_fn.constprop':
>>> arch/csky/include/asm/uaccess.h:147:9: warning: 'retval' is used uninitialized [-Wuninitialized]
> 147 | __asm__ __volatile__( \
> | ^~~~~~~
> arch/csky/include/asm/uaccess.h:187:17: note: in expansion of macro '__get_user_asm_64'
> 187 | __get_user_asm_64(x, ptr, retval);
> | ^~~~~~~~~~~~~~~~~
> arch/csky/include/asm/uaccess.h:170:13: note: 'retval' was declared here
> 170 | int retval;
> | ^~~~~~
>
>
> vim +/retval +147 arch/csky/include/asm/uaccess.h
>
> da551281947cb2c Guo Ren 2018-09-05 141
> e58a41c2226847f Guo Ren 2021-04-21 142 #define __get_user_asm_64(x, ptr, err) \
> da551281947cb2c Guo Ren 2018-09-05 143 do { \
> da551281947cb2c Guo Ren 2018-09-05 144 int tmp; \
> e58a41c2226847f Guo Ren 2021-04-21 145 int errcode; \
> e58a41c2226847f Guo Ren 2021-04-21 146 \
> e58a41c2226847f Guo Ren 2021-04-21 @147 __asm__ __volatile__( \
> e58a41c2226847f Guo Ren 2021-04-21 148 "1: ldw %3, (%2, 0) \n" \
> da551281947cb2c Guo Ren 2018-09-05 149 " stw %3, (%1, 0) \n" \
> e58a41c2226847f Guo Ren 2021-04-21 150 "2: ldw %3, (%2, 4) \n" \
> e58a41c2226847f Guo Ren 2021-04-21 151 " stw %3, (%1, 4) \n" \
> e58a41c2226847f Guo Ren 2021-04-21 152 " br 4f \n" \
> e58a41c2226847f Guo Ren 2021-04-21 153 "3: mov %0, %4 \n" \
> e58a41c2226847f Guo Ren 2021-04-21 154 " br 4f \n" \
> da551281947cb2c Guo Ren 2018-09-05 155 ".section __ex_table, \"a\" \n" \
> da551281947cb2c Guo Ren 2018-09-05 156 ".align 2 \n" \
> e58a41c2226847f Guo Ren 2021-04-21 157 ".long 1b, 3b \n" \
> e58a41c2226847f Guo Ren 2021-04-21 158 ".long 2b, 3b \n" \
> da551281947cb2c Guo Ren 2018-09-05 159 ".previous \n" \
> e58a41c2226847f Guo Ren 2021-04-21 160 "4: \n" \
> e58a41c2226847f Guo Ren 2021-04-21 161 : "=r"(err), "=r"(x), "=r"(ptr), \
> e58a41c2226847f Guo Ren 2021-04-21 162 "=r"(tmp), "=r"(errcode) \
> e58a41c2226847f Guo Ren 2021-04-21 163 : "0"(err), "1"(x), "2"(ptr), "3"(0), \
> e58a41c2226847f Guo Ren 2021-04-21 164 "4"(-EFAULT) \
> da551281947cb2c Guo Ren 2018-09-05 165 : "memory"); \
> da551281947cb2c Guo Ren 2018-09-05 166 } while (0)
> da551281947cb2c Guo Ren 2018-09-05 167

The intel test report reported the above compile warning on this series:

https://lore.kernel.org/netdev/20250627084609-mutt-send-email-mst@kernel.org/T/#md788de2b3a4e9da23ac93b5f1c773a6070b5b4fb

specifically, in patch 4:

+ if (get_user(features, featurep + 1 + i))
+ return -EFAULT;

AFAICS such statement is legit, and the bot points to some problem in
the arch specific get_user() implementation. Could you please have a look?

Thanks,

Paolo