Re: drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative

From: Zi Yan
Date: Thu Mar 23 2023 - 07:51:42 EST

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In reply to: kernel test robot: "drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative"
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On 23 Mar 2023, at 7:12, kernel test robot wrote:

> Hi Zi,
>
> 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/torvalds/linux.git master
> head: fff5a5e7f528b2ed2c335991399a766c2cf01103
> commit: 0192445cb2f7ed1cd7a95a0fc8c7645480baba25 arch: mm: rename FORCE_MAX_ZONEORDER to ARCH_FORCE_MAX_ORDER
> date: 6 months ago
> config: sparc-randconfig-r005-20230322 (https://download.01.org/0day-ci/archive/20230323/202303231958.9lByNCPW-lkp@xxxxxxxxx/config)

It is the same issue as: https://lore.kernel.org/linux-mm/91E887E4-0867-421F-9C75-FB9CFF15C33A@xxxxxxxxxx/

> compiler: sparc-linux-gcc (GCC) 12.1.0
> 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
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0192445cb2f7ed1cd7a95a0fc8c7645480baba25
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git fetch --no-tags linus master
> git checkout 0192445cb2f7ed1cd7a95a0fc8c7645480baba25
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sparc olddefconfig
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sparc SHELL=/bin/bash drivers/base/regmap/ drivers/virtio/
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Link: https://lore.kernel.org/oe-kbuild-all/202303231958.9lByNCPW-lkp@xxxxxxxxx/
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/gfp.h:7,
> from include/linux/mm.h:7,
> from include/linux/scatterlist.h:8,
> from include/linux/virtio.h:7,
> from drivers/virtio/virtio_balloon.c:9:
> include/linux/mmzone.h:636:33: error: size of array 'free_area' is negative
> 636 | struct free_area free_area[MAX_ORDER];
> | ^~~~~~~~~
> In file included from include/linux/math64.h:6,
> from include/linux/time64.h:5,
> from include/linux/restart_block.h:10,
> from include/linux/thread_info.h:14,
> from include/asm-generic/preempt.h:5,
> from ./arch/sparc/include/generated/asm/preempt.h:1,
> from include/linux/preempt.h:78,
> from include/linux/spinlock.h:55,
> from include/linux/mmzone.h:8:
> drivers/virtio/virtio_balloon.c: In function 'shrink_free_pages':
>>> drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative [-Wshift-count-negative]
> 40 | #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
> | ^~
> include/linux/math.h:15:46: note: in definition of macro '__round_mask'
> 15 | #define __round_mask(x, y) ((__typeof__(x))((y)-1))
> | ^
> drivers/virtio/virtio_balloon.c:808:25: note: in expansion of macro 'round_up'
> 808 | pages_to_free = round_up(pages_to_free,
> | ^~~~~~~~
> drivers/virtio/virtio_balloon.c:809:34: note: in expansion of macro 'VIRTIO_BALLOON_HINT_BLOCK_PAGES'
> 809 | VIRTIO_BALLOON_HINT_BLOCK_PAGES);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative [-Wshift-count-negative]
> 40 | #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
> | ^~
> drivers/virtio/virtio_balloon.c:810:42: note: in expansion of macro 'VIRTIO_BALLOON_HINT_BLOCK_PAGES'
> 810 | blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative [-Wshift-count-negative]
> 40 | #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
> | ^~
> drivers/virtio/virtio_balloon.c:813:31: note: in expansion of macro 'VIRTIO_BALLOON_HINT_BLOCK_PAGES'
> 813 | return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/virtio/virtio_balloon.c: In function 'virtio_balloon_shrinker_count':
>>> drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative [-Wshift-count-negative]
> 40 | #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
> | ^~
> drivers/virtio/virtio_balloon.c:831:43: note: in expansion of macro 'VIRTIO_BALLOON_HINT_BLOCK_PAGES'
> 831 | return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> --
> In file included from include/linux/gfp.h:7,
> from include/linux/slab.h:15,
> from drivers/base/regmap/regmap-debugfs.c:9:
> include/linux/mmzone.h:636:33: error: size of array 'free_area' is negative
> 636 | struct free_area free_area[MAX_ORDER];
> | ^~~~~~~~~
> drivers/base/regmap/regmap-debugfs.c: In function 'regmap_read_debugfs':
>>> drivers/base/regmap/regmap-debugfs.c:229:32: warning: left shift count is negative [-Wshift-count-negative]
> 229 | if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
> | ^~
> drivers/base/regmap/regmap-debugfs.c:230:35: warning: left shift count is negative [-Wshift-count-negative]
> 230 | count = PAGE_SIZE << (MAX_ORDER - 1);
> | ^~
> drivers/base/regmap/regmap-debugfs.c: In function 'regmap_reg_ranges_read_file':
> drivers/base/regmap/regmap-debugfs.c:376:32: warning: left shift count is negative [-Wshift-count-negative]
> 376 | if (count > (PAGE_SIZE << (MAX_ORDER - 1)))
> | ^~
> drivers/base/regmap/regmap-debugfs.c:377:35: warning: left shift count is negative [-Wshift-count-negative]
> 377 | count = PAGE_SIZE << (MAX_ORDER - 1);
> | ^~
>
>
> vim +40 drivers/virtio/virtio_balloon.c
>
> 5a10b7dbf904bf Raushaniya Maksudova 2014-11-10 32
> 86a559787e6f5c Wei Wang 2018-08-27 33 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
> 86a559787e6f5c Wei Wang 2018-08-27 34 __GFP_NOMEMALLOC)
> 86a559787e6f5c Wei Wang 2018-08-27 35 /* The order of free page blocks to report to host */
> 2a946fa1c8bc26 Michael S. Tsirkin 2019-11-19 36 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
> 86a559787e6f5c Wei Wang 2018-08-27 37 /* The size of a free page block in bytes */
> 2a946fa1c8bc26 Michael S. Tsirkin 2019-11-19 38 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
> 2a946fa1c8bc26 Michael S. Tsirkin 2019-11-19 39 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
> 63b9b80e9f5b2c Michael S. Tsirkin 2019-11-19 @40 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
> 86a559787e6f5c Wei Wang 2018-08-27 41
>
> :::::: The code at line 40 was first introduced by commit
> :::::: 63b9b80e9f5b2c463d98d6e550e0d0e3ace66033 virtio_balloon: divide/multiply instead of shifts
>
> :::::: TO: Michael S. Tsirkin <mst@xxxxxxxxxx>
> :::::: CC: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests

--
Best Regards,
Yan, Zi

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Next message: Suzuki K Poulose: "Re: [PATCH v3 02/11] coresight-tpda: Add DSB dataset support"
Previous message: Christian Brauner: "Re: [PATCH 1/1] vhost_task: Fix vhost_task_create return value"
In reply to: kernel test robot: "drivers/virtio/virtio_balloon.c:40:44: warning: left shift count is negative"
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