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Message-ID: <27f1275a-aaff-4cc2-896c-b2c34f08ab73@redhat.com>
Date: Fri, 27 Jun 2025 16:36:14 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: kernel test robot <lkp@...el.com>, netdev@...r.kernel.org,
Guo Ren <guoren@...nel.org>, linux-csky@...r.kernel.org
Cc: oe-kbuild-all@...ts.linux.dev,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Jason Wang <jasowang@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
"Michael S. Tsirkin" <mst@...hat.com>, Xuan Zhuo
<xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
<eperezma@...hat.com>, Yuri Benditovich <yuri.benditovich@...nix.com>,
Akihiko Odaki <akihiko.odaki@...nix.com>, Jonathan Corbet <corbet@....net>,
kvm@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 net-next 4/9] vhost-net: allow configuring extended
features
On 6/27/25 3:11 PM, Paolo Abeni wrote:
> +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@...el.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?
Out of sheer ignorance on my side, I fail to see how the csky get_user()
could work correctly without something alike the following (which indeed
fixes the issue here).
/P
---
diff --git a/arch/csky/include/asm/uaccess.h
b/arch/csky/include/asm/uaccess.h
index 2e927c21d8a1..ae0864ad59a3 100644
--- a/arch/csky/include/asm/uaccess.h
+++ b/arch/csky/include/asm/uaccess.h
@@ -167,7 +167,7 @@ do { \
static inline int __get_user_fn(size_t size, const void __user *ptr,
void *x)
{
- int retval;
+ int retval = 0;
u32 tmp;
switch (size) {
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