* [linux-next:master 10286/12016] arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used
@ 2023-04-17 12:55 kernel test robot
2023-04-17 13:49 ` Mark Rutland
0 siblings, 1 reply; 3+ messages in thread
From: kernel test robot @ 2023-04-17 12:55 UTC (permalink / raw)
To: Mark Rutland
Cc: llvm, oe-kbuild-all, Linux Memory Management List, Will Deacon,
Ryan Roberts
Hi Mark,
FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head: d3f2cd24819158bb70701c3549e586f9df9cee67
commit: b97547761b02cc95e0e6be827dc9ca9da8142761 [10286/12016] arm64: mm: move fixmap code to its own file
config: arm64-buildonly-randconfig-r004-20230416 (https://download.01.org/0day-ci/archive/20230417/202304172004.r3IPh5Ja-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 9638da200e00bd069e6dd63604e14cbafede9324)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install arm64 cross compiling tool for clang build
# apt-get install binutils-aarch64-linux-gnu
# https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=b97547761b02cc95e0e6be827dc9ca9da8142761
git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
git fetch --no-tags linux-next master
git checkout b97547761b02cc95e0e6be827dc9ca9da8142761
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash arch/arm64/mm/
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304172004.r3IPh5Ja-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used [-Wunused-but-set-variable]
pud_t *bm_pudp;
^
1 warning generated.
vim +/bm_pudp +199 arch/arm64/mm/fixmap.c
182
183 /*
184 * Copy the fixmap region into a new pgdir.
185 */
186 void __init fixmap_copy(pgd_t *pgdir)
187 {
188 if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdir, FIXADDR_TOT_START)))) {
189 /*
190 * The fixmap falls in a separate pgd to the kernel, and doesn't
191 * live in the carveout for the swapper_pg_dir. We can simply
192 * re-use the existing dir for the fixmap.
193 */
194 set_pgd(pgd_offset_pgd(pgdir, FIXADDR_TOT_START),
195 READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
196 } else if (CONFIG_PGTABLE_LEVELS > 3) {
197 pgd_t *bm_pgdp;
198 p4d_t *bm_p4dp;
> 199 pud_t *bm_pudp;
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [linux-next:master 10286/12016] arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used
2023-04-17 12:55 [linux-next:master 10286/12016] arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used kernel test robot
@ 2023-04-17 13:49 ` Mark Rutland
2023-04-19 6:06 ` Yujie Liu
0 siblings, 1 reply; 3+ messages in thread
From: Mark Rutland @ 2023-04-17 13:49 UTC (permalink / raw)
To: kernel test robot
Cc: llvm, oe-kbuild-all, Linux Memory Management List, Will Deacon,
Ryan Roberts
On Mon, Apr 17, 2023 at 08:55:17PM +0800, kernel test robot wrote:
> Hi Mark,
Hi,
> FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
I took a look, and this warning existed in the prior commit. All that has
changed is that it has moved from arch/arm64/mm/mmu.c to arch/arm64/mm/init.c.
This commit is not to blame, and there is no regression here.
The warning itself is bogus; more details on that below. Please ignore this.
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head: d3f2cd24819158bb70701c3549e586f9df9cee67
> commit: b97547761b02cc95e0e6be827dc9ca9da8142761 [10286/12016] arm64: mm: move fixmap code to its own file
> config: arm64-buildonly-randconfig-r004-20230416 (https://download.01.org/0day-ci/archive/20230417/202304172004.r3IPh5Ja-lkp@intel.com/config)
> compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 9638da200e00bd069e6dd63604e14cbafede9324)
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # install arm64 cross compiling tool for clang build
> # apt-get install binutils-aarch64-linux-gnu
> # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=b97547761b02cc95e0e6be827dc9ca9da8142761
> git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> git fetch --no-tags linux-next master
> git checkout b97547761b02cc95e0e6be827dc9ca9da8142761
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash arch/arm64/mm/
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Link: https://lore.kernel.org/oe-kbuild-all/202304172004.r3IPh5Ja-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> >> arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used [-Wunused-but-set-variable]
> pud_t *bm_pudp;
> ^
> 1 warning generated.
>
>
> vim +/bm_pudp +199 arch/arm64/mm/fixmap.c
>
:> 182
> 183 /*
> 184 * Copy the fixmap region into a new pgdir.
> 185 */
> 186 void __init fixmap_copy(pgd_t *pgdir)
> 187 {
> 188 if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdir, FIXADDR_TOT_START)))) {
> 189 /*
> 190 * The fixmap falls in a separate pgd to the kernel, and doesn't
> 191 * live in the carveout for the swapper_pg_dir. We can simply
> 192 * re-use the existing dir for the fixmap.
> 193 */
> 194 set_pgd(pgd_offset_pgd(pgdir, FIXADDR_TOT_START),
> 195 READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
> 196 } else if (CONFIG_PGTABLE_LEVELS > 3) {
> 197 pgd_t *bm_pgdp;
> 198 p4d_t *bm_p4dp;
> > 199 pud_t *bm_pudp;
The full piece of code in question is:
| } else if (CONFIG_PGTABLE_LEVELS > 3) {
| pgd_t *bm_pgdp;
| p4d_t *bm_p4dp;
| pud_t *bm_pudp;
^ defined
| /*
| * The fixmap shares its top level pgd entry with the kernel
| * mapping. This can really only occur when we are running
| * with 16k/4 levels, so we can simply reuse the pud level
| * entry instead.
| */
| BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
| bm_pgdp = pgd_offset_pgd(pgdp, FIXADDR_TOT_START);
| bm_p4dp = p4d_offset(bm_pgdp, FIXADDR_TOT_START);
| bm_pudp = pud_set_fixmap_offset(bm_p4dp, FIXADDR_TOT_START);
^ set
| pud_populate(&init_mm, bm_pudp, lm_alias(bm_pmd));
^ used
| pud_clear_fixmap();
| } else {
What's happening here is that the config has CONFIG_PGTABLE_LEVELS=2, where the
above block is unreachable, but the warning is being generated for trivially
unreachable code.
With that config, we'll use include/asm-generic/pgtable-nopmd.h, where
pud_populate() is defined as:
| #define pud_populate(mm, pmd, pte) do { } while (0)
... and hence it's complaing that the (unreachable) definition and
initialization of bm_pudp is not used.
If I reconfigure the kernel with 4K pages and 48-bit VAs so that
CONFIG_PGTABLE_LEVELS=4, the above warning isn't generated.
Thanks,
Mark.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [linux-next:master 10286/12016] arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used
2023-04-17 13:49 ` Mark Rutland
@ 2023-04-19 6:06 ` Yujie Liu
0 siblings, 0 replies; 3+ messages in thread
From: Yujie Liu @ 2023-04-19 6:06 UTC (permalink / raw)
To: Mark Rutland
Cc: kernel test robot, llvm, oe-kbuild-all,
Linux Memory Management List, Will Deacon, Ryan Roberts
On Mon, Apr 17, 2023 at 02:49:57PM +0100, Mark Rutland wrote:
> On Mon, Apr 17, 2023 at 08:55:17PM +0800, kernel test robot wrote:
> > Hi Mark,
>
> Hi,
>
> > FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
>
> I took a look, and this warning existed in the prior commit. All that has
> changed is that it has moved from arch/arm64/mm/mmu.c to arch/arm64/mm/init.c.
>
> This commit is not to blame, and there is no regression here.
>
> The warning itself is bogus; more details on that below. Please ignore this.
Sorry for this false positive. We've configured the bot to filter out
the reports on this commit.
Best Regards,
Yujie
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head: d3f2cd24819158bb70701c3549e586f9df9cee67
> > commit: b97547761b02cc95e0e6be827dc9ca9da8142761 [10286/12016] arm64: mm: move fixmap code to its own file
> > config: arm64-buildonly-randconfig-r004-20230416 (https://download.01.org/0day-ci/archive/20230417/202304172004.r3IPh5Ja-lkp@intel.com/config)
> > compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 9638da200e00bd069e6dd63604e14cbafede9324)
> > reproduce (this is a W=1 build):
> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # install arm64 cross compiling tool for clang build
> > # apt-get install binutils-aarch64-linux-gnu
> > # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=b97547761b02cc95e0e6be827dc9ca9da8142761
> > git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> > git fetch --no-tags linux-next master
> > git checkout b97547761b02cc95e0e6be827dc9ca9da8142761
> > # save the config file
> > mkdir build_dir && cp config build_dir/.config
> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash arch/arm64/mm/
> >
> > If you fix the issue, kindly add following tag where applicable
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Link: https://lore.kernel.org/oe-kbuild-all/202304172004.r3IPh5Ja-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used [-Wunused-but-set-variable]
> > pud_t *bm_pudp;
> > ^
> > 1 warning generated.
> >
> >
> > vim +/bm_pudp +199 arch/arm64/mm/fixmap.c
> >
> :> 182
> > 183 /*
> > 184 * Copy the fixmap region into a new pgdir.
> > 185 */
> > 186 void __init fixmap_copy(pgd_t *pgdir)
> > 187 {
> > 188 if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdir, FIXADDR_TOT_START)))) {
> > 189 /*
> > 190 * The fixmap falls in a separate pgd to the kernel, and doesn't
> > 191 * live in the carveout for the swapper_pg_dir. We can simply
> > 192 * re-use the existing dir for the fixmap.
> > 193 */
> > 194 set_pgd(pgd_offset_pgd(pgdir, FIXADDR_TOT_START),
> > 195 READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
> > 196 } else if (CONFIG_PGTABLE_LEVELS > 3) {
> > 197 pgd_t *bm_pgdp;
> > 198 p4d_t *bm_p4dp;
> > > 199 pud_t *bm_pudp;
>
> The full piece of code in question is:
>
> | } else if (CONFIG_PGTABLE_LEVELS > 3) {
> | pgd_t *bm_pgdp;
> | p4d_t *bm_p4dp;
> | pud_t *bm_pudp;
> ^ defined
>
> | /*
> | * The fixmap shares its top level pgd entry with the kernel
> | * mapping. This can really only occur when we are running
> | * with 16k/4 levels, so we can simply reuse the pud level
> | * entry instead.
> | */
> | BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
> | bm_pgdp = pgd_offset_pgd(pgdp, FIXADDR_TOT_START);
> | bm_p4dp = p4d_offset(bm_pgdp, FIXADDR_TOT_START);
> | bm_pudp = pud_set_fixmap_offset(bm_p4dp, FIXADDR_TOT_START);
> ^ set
>
> | pud_populate(&init_mm, bm_pudp, lm_alias(bm_pmd));
> ^ used
>
> | pud_clear_fixmap();
> | } else {
>
> What's happening here is that the config has CONFIG_PGTABLE_LEVELS=2, where the
> above block is unreachable, but the warning is being generated for trivially
> unreachable code.
>
> With that config, we'll use include/asm-generic/pgtable-nopmd.h, where
> pud_populate() is defined as:
>
> | #define pud_populate(mm, pmd, pte) do { } while (0)
>
> ... and hence it's complaing that the (unreachable) definition and
> initialization of bm_pudp is not used.
>
> If I reconfigure the kernel with 4K pages and 48-bit VAs so that
> CONFIG_PGTABLE_LEVELS=4, the above warning isn't generated.
>
> Thanks,
> Mark.
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-04-19 6:09 UTC | newest]
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2023-04-17 12:55 [linux-next:master 10286/12016] arch/arm64/mm/fixmap.c:199:10: warning: variable 'bm_pudp' set but not used kernel test robot
2023-04-17 13:49 ` Mark Rutland
2023-04-19 6:06 ` Yujie Liu
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